US20050215207A1 - Method and system for frequency up-conversion with a variety of transmitter configurations - Google Patents

Abstract

A method and system is described wherein a signal with a lower frequency is up-converted to a higher frequency. In one embodiment, the higher frequency signal is used as a stable frequency and phase reference. In another embodiment, the invention is used as a transmitter. The up-conversion is accomplished by controlling a switch with an oscillating signal, the frequency of the oscillating signal being selected as a sub-harmonic of the desired output frequency. When the invention is being used as a frequency or phase reference, the oscillating signal is not modulated, and controls a switch that is connected to a bias signal. When the invention is being used in the frequency modulation (FM) or phase modulation (PM) implementations, the oscillating signal is modulated by an information signal before it causes the switch to gate the bias signal. In the amplitude modulation implementation (AM), the oscillating signal is not modulated, but rather causes the switch to gate a reference signal that is substantially equal to or proportional to the information signal. In the FM and PM implementations, the signal that is output from the switch is modulated substantially the same as the modulated oscillating signal. In the AM implementation, the signal that is output from the switch has an amplitude that is a function of the information signal. In both embodiments, the output of the switch is filtered, and the desired harmonic is output.

Description

CROSS-REFERENCE TO OTHER APPLICATIONS
• This is a continuation-in-part application of pending U.S. application “Method and System for Frequency Up-Conversion,” Ser. No. 09/176,154, filed Oct. 21, 1998, Attorney Docket No. 1744.0020000, which is incorporated herein by reference in its entirety.
• The following applications of common assignee are related to the present application, and are herein incorporated by reference in their entireties:
• • “Method and System for Down-Converting Electromagnetic Signals,” Ser. No. 09/176,022, filed Oct. 21, 1998, Attorney Docket No. 1744.0010000.
  • “Method and System for Ensuring Reception of a Communications Signal,” Ser. No. 09/176,415, filed Oct. 21, 1998, Attorney Docket No. 1744.0030000.
  • “Integrated Frequency Translation and Selectivity,” Ser. No. 09/175,966, filed Oct. 21, 1998, Attorney Docket No. 1744.0130000.
  • “Universal Frequency Translation, and Applications of Same,” Ser. No. 09/176,027, filed Oct. 21, 1998, Attorney Docket No. 1744.0140000.
  • “Method and System for Down-Converting Electromagnetic Signals Having Optimized Switch Structures,” Ser. No. TBD, filed Apr. 16, 1999,
  • “Method and System for Down-Converting Electromagnetic Signals Including Resonant Structures for Enhanced Energy Transfer,” Ser. No. TBD, filed Apr. 16, 1999, Attorney Docket No. 1744.0010002.
  • “Method and System for Frequency Up-Conversion Having Optimized Switch Structures,” Ser. No. TBD, filed Apr. 16, 1999, Attorney Docket No. 1744.0020001.
  • “Integrated Frequency Translation And Selectivity With a Variety of Filter Embodiments,” Ser. No. TBD, filed Apr. 16, 1999, Attorney Docket No. 1744.0130001.
  • “Frequency Translator Having a Controlled Aperture Sub-Harmonic Matched Filter,” Ser. No. TBD, filed Apr. 16, 1999, Attorney Docket No. 1744.0520000.
BACKGROUND OF THE INVENTION
• 1. Field of the Invention
• The present invention is generally directed to frequency up-conversion of electromagnetic (EM) signals.
• 2. Related Art
• Modern day communication systems employ components such as transmitters and receivers to transmit information from a source to a destination. To accomplish this transmission, information is imparted on a carrier signal and the carrier signal is then transmitted. Typically, the carrier signal is at a frequency higher than the baseband frequency of the information signal. Typical ways that the information is imparted on the carrier signal are called modulation.
• Three widely used modulation schemes include: frequency modulation (FM), where the frequency of the carrier wave changes to reflect the information that has been modulated on the signal; phase modulation (PM), where the phase of the carrier signal changes to reflect the information imparted on it; and amplitude modulation (AM), where the amplitude of the carrier signal changes to reflect the information. Also, these modulation schemes are used in combination with each other (e.g., AM combined with FM and AM combined with PM).
SUMMARY OF THE INVENTION
• The present invention is directed to methods and systems to up-convert a signal from a lower frequency to a higher frequency, and applications thereof.
• In one embodiment, the invention uses a stable, low frequency signal to generate a higher frequency signal with a frequency and phase that can be used as stable references.
• In another embodiment, the present invention is used as a transmitter. In this embodiment, the invention accepts an information signal at a baseband frequency and transmits a modulated signal at a frequency higher than the baseband frequency.
• The methods and systems of transmitting vary slightly depending on the modulation scheme being used. For some embodiments using frequency modulation (FM) or phase modulation (PM), the information signal is used to modulate an oscillating signal to create a modulated intermediate signal. If needed, this modulated intermediate signal is “shaped” to provide a substantially optimum pulse-width-to-period ratio. This shaped signal is then used to control a switch which opens and closes as a function of the frequency and pulse width of the shaped signal. As a result of this opening and closing, a signal that is harmonically rich is produced with each harmonic of the harmonically rich signal being modulated substantially the same as the modulated intermediate signal. Through proper filtering, the desired harmonic (or harmonics) is selected and transmitted.
• For some embodiments using amplitude modulation (AM), the switch is controlled by an unmodulated oscillating signal (which may, if needed, be shaped). As the switch opens and closes, it gates a reference signal which is the information signal. In an alternate implementation, the information signal is combined with a bias signal to create the reference signal, which is then gated. The result of the gating is a harmonically rich signal having a fundamental frequency substantially proportional to the oscillating signal and an amplitude substantially proportional to the amplitude of the reference signal. Each of the harmonics of the harmonically rich signal also have amplitudes proportional to the reference signal, and are thus considered to be amplitude modulated. Just as with the FM/PM embodiments described above, through proper filtering, the desired harmonic (or harmonics) is selected and transmitted.
• Further features and advantages of the invention, as well as the structure and operation of various embodiments of the invention, are described in detail below with reference to the accompanying figures. The left-most digit(s) of a reference number typically identifies the figure in which the reference number first appears.
BRIEF DESCRIPTION OF THE FIGURES
• FIG. 1 illustrates a circuit for a frequency modulation (FM) transmitter;
• FIGS. 2A, 2B, and2C illustrate typical waveforms associated with theFIG. 1 FM circuit for a digital information signal;
• FIG. 3 illustrates a circuit for a phase modulation (PM) transmitter;
• FIGS. 4A, 4B, and4C illustrate typical waveforms associated with theFIG. 3 PM circuit for a digital information signal;
• FIG. 5 illustrates a circuit for an amplitude modulation (AM) transmitter;
• FIGS. 6A, 6B, and6C illustrate typical waveforms associated with theFIG. 5 AM circuit for a digital information signal;
• FIG. 7 illustrates a circuit for an in-phase/quadrature-phase modulation (“I/Q”) transmitter;
• FIGS. 8A, 8B,8C,8D, and8E illustrate typical waveforms associated with theFIG. 7 “I/Q” circuit for digital information signal;
• FIG. 9 illustrates the high level operational flowchart of a transmitter according to an embodiment of the present invention;
• FIG. 10 illustrates the high level structural block diagram of the transmitter of an embodiment of the present invention;
• FIG. 11 illustrates the operational flowchart of a first embodiment (i.e., FM mode) of the present invention;
• FIG. 12 illustrates an exemplary structural block diagram of the first embodiment (i.e., FM mode) of the present invention;
• FIG. 13 illustrates the operational flowchart of a second embodiment (i.e., PM mode) of the present invention;
• FIG. 14 illustrates an exemplary structural block diagram of the second embodiment (i.e., PM mode) of the present invention;
• FIG. 15 illustrates the operational flowchart of a third embodiment (i.e., AM mode) of the present invention;
• FIG. 16 illustrates an exemplary structural block diagram of the third embodiment (i.e., AM mode) of the present invention;
• FIG. 17 illustrates the operational flowchart of a fourth embodiment (i.e., “I/Q” mode) of the present invention;
• FIG. 18 illustrates an exemplary structural block diagram of the fourth embodiment (i.e., “I/Q” mode) of the present invention;
• FIGS. 19A-19I illustrate exemplary waveforms (for a frequency modulation mode operating in a frequency shift keying embodiment) at a plurality of points in an exemplary high level circuit diagram;
• FIGS. 20A, 20B,20C illustrate typical waveforms associated with theFIG. 1 FM circuit for an analog information signal;
• FIGS. 21A, 21B,21C illustrate typical waveforms associated with theFIG. 3 PM circuit for an analog information signal;
• FIGS. 22A, 22B,22C illustrate typical waveforms associated with theFIG. 5 AM circuit for an analog information signal;
• FIG. 23 illustrates an implementation example of a voltage controlled oscillator (VCO);
• FIG. 24 illustrates an implementation example of a local oscillator (LO);
• FIG. 25 illustrates an implementation example of a phase shifter;
• FIG. 26 illustrates an implementation example of a phase modulator;
• FIG. 27 illustrates an implementation example of a summing amplifier;
• FIGS. 28A-28C illustrate an implementation example of a switch module for the FM and PM modes;
• FIG. 29A-29C illustrate an example of the switch module ofFIGS. 28A-28C wherein the switch is a GaAsFET;
• FIGS. 30A-30C illustrate an example of a design to ensure symmetry for a GaAsFET implementation in the FM and PM modes;
• FIGS. 31A-31C illustrate an implementation example of a switch module for the AM mode;
• FIGS. 32A-31C illustrate the switch module ofFIGS. 31A-31C wherein the switch is a GaAsFET;
• FIGS. 33A-33C illustrates an example of a design to ensure symmetry for a GaAsFET implementation in the AM mode;
• FIG. 34 illustrates an implementation example of a summer;
• FIG. 35 illustrates an implementation example of a filter;
• FIG. 36 is a representative spectrum demonstrating the calculation of “Q;”
• FIGS. 37A and 37B are representative examples of filter circuits;
• FIG. 38 illustrates an implementation example of a transmission module;
• FIG. 39A shows a first exemplary pulse shaping circuit using digital logic devices for a squarewave input from an oscillator;
• FIGS. 39B, 39C, and39D illustrate waveforms associated with theFIG. 39A circuit;
• FIG. 40A shows a second exemplary pulse shaping circuit using digital logic devices for a squarewave input from an oscillator;
• FIGS. 40B, 40C, and40D illustrate waveforms associated with theFIG. 40A circuit;
• FIG. 41 shows a third exemplary pulse shaping circuit for any input from an oscillator;
• FIGS. 42A, 42B,42C,42D, and42E illustrate representative waveforms associated with theFIG. 41 circuit;
• FIG. 43 shows the internal circuitry for elements ofFIG. 41 according to an embodiment of the invention;
• FIGS. 44A-44G illustrate exemplary waveforms (for a pulse modulation mode operating in a pulse shift keying embodiment) at a plurality of points in an exemplary high level circuit diagram, highlighting the characteristics of the first three harmonics;
• FIGS. 45A-45F illustrate exemplary waveforms (for an amplitude modulation mode operating in an amplitude shift keying embodiment) at a plurality of points in an exemplary high level circuit diagram, highlighting the characteristics of the first three harmonics;
• FIG. 46 illustrates an implementation example of a harmonic enhancement module;
• FIG. 47 illustrates an implementation example of an amplifier module;
• FIGS. 48A and 48B illustrate exemplary circuits for a linear amplifier;
• FIG. 49 illustrates a typical superheterodyne receiver;
• FIG. 50 illustrates a transmitter according to an embodiment of the present invention in a transceiver circuit with a typical superheterodyne receiver in a full-duplex mode;
• FIGS. 51A, 51B,51C, and51D illustrate a transmitter according to an embodiment of the present invention in a transceiver circuit using a common oscillator with a typical superheterodyne receiver in a half-duplex mode;
• FIG. 52 illustrates an exemplary receiver using universal frequency down conversion techniques according to an embodiment;
• FIG. 53 illustrates an exemplary transmitter of the present invention;
• FIGS. 54A, 54B, and54C illustrate an exemplary transmitter of the present invention in a transceiver circuit with a universal frequency down conversion receiver operating in a half-duplex mode for the FM and PM modulation embodiment;
• FIG. 55 illustrates an exemplary transmitter of the present invention in a transceiver circuit with a universal frequency down conversion receiver operating in a half-duplex mode for the AM modulation embodiment;
• FIG. 56 illustrates an exemplary transmitter of the present invention in a transceiver circuit with a universal frequency down conversion receiver operating in a full-duplex mode;
• FIGS. 57A-57C illustrate an exemplary transmitter of the present invention being used in frequency modulation, phase modulation, and amplitude modulation embodiments, including a pulse shaping circuit and an amplifier module;
• FIG. 58 illustrates harmonic amplitudes for a pulse-width-to-period ratio of 0.01;
• FIG. 59 illustrates harmonic amplitudes for a pulse-width-to-period ratio of 0.0556;
• FIG. 60 is a table that illustrates the relative amplitudes of the first 50 harmonics for six exemplary pulse-width-to-period ratios;
• FIG. 61 is a table that illustrates the relative amplitudes of the first 25 harmonics for six pulse-width-to-period ratios optimized for the 1^stthrough 10^thsubharmonics;
• FIG. 62 illustrates an exemplary structural block diagram for an alternative embodiment of the present invention (i.e., a mode wherein AM is combined with PM);
• FIGS. 63A-63H illustrate exemplary waveforms (for the embodiment ofFIG. 62) at a plurality of points in an exemplary high level circuit diagram, highlighting the characteristics of the first two harmonics;
• FIGS.64A and64A1 illustrate exemplary implementations of aliasing modules;
• FIGS. 64B-64F illustrate exemplary waveforms at a plurality of points in the FIGS.64A and64A1 circuits;
• FIG. 65—intentionally left blank;
• FIG. 66—intentionally left blank;
• FIG. 67—intentionally left blank;
• FIG. 68—intentionally left blank;
• FIG. 69—intentionally left blank;
• FIG. 70—intentionally left blank;
• FIG. 71—intentionally left blank;
• FIG. 72A is a block diagram of a splitter according to an embodiment of the invention;
• FIG. 72B is a more detailed diagram of a splitter according to an embodiment of the invention;
• FIGS. 72C and 72D are example waveforms related to the splitter ofFIGS. 72A and 72B;
• FIG. 72E is a block diagram of an I/Q circuit with a splitter according to an embodiment of the invention;
• FIGS. 72F-72J are example waveforms related to the diagram ofFIG. 72A;
• FIG. 73 is a block diagram of a switch module according to an embodiment of the invention;
• FIG. 74A is an implementation example of the block diagram ofFIG. 73;
• FIGS. 74B-74Q are example waveforms related toFIG. 74A;
• FIG. 75A is another implementation example of the block diagram ofFIG. 73;
• FIGS. 75B-75Q are example waveforms related toFIG. 75A;
• FIG. 76A is an example MOSFET embodiment of the invention;
• FIG. 76B is an example MOSFET embodiment of the invention;
• FIG. 76C is an example MOSFET embodiment of the invention;
• FIG. 77A is another implementation example of the block diagram ofFIG. 73;
• FIGS. 77B-77Q are example waveforms related toFIG. 75A;
• FIG. 78 illustrates an implementation of the present invention wherein multiple apertures are generated for each cycle of an oscillating signal;
• FIG. 79 illustrates the multiple aperture generation module;
• FIG. 80 illustrates exemplary waveforms for strings of pulses containing from one pulse through five pulses per cycle;
• FIG. 81 illustrates the output spectra for one pulse per cycle;
• FIG. 82 illustrates the output spectra for two pulses per cycle;
• FIG. 83 illustrates the output spectra for three pulses per cycle;
• FIG. 84 illustrates the output spectra for four pulses per cycle;
• FIG. 85 illustrates the output spectra for five pulses per cycle;
• FIG. 86 compares the amplitudes of the output spectra at the desired output frequency;
• FIG. 87 illustrates a circuit diagram for the bi-polar pulses;
• FIG. 88 illustrates the spectra resulting from the use of bi-polar pulses;
• FIG. 89 illustrates the bi-polar pulse stream; and
• FIG. 90 illustrates the orignal pulse stream used to generate the bi-polar pulse stream.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

• Table ofcontents

  1.	Terminology.
  2.	Overview of the Invention.

  	2.1	Discussion of Modulation Techniques.
  	2.2	Explanation of Exemplary Circuits and Waveforms.

  		2.2.1	Frequency Modulation.
  		2.2.2	Phase Modulation.
  		2.2.3	Amplitude Modulation.
  		2.2.4	In-phase/Quadrature-phase Modulation.

  2.3

  Features of the Invention.

  3.	Frequency Up-conversion.

  3.1

  High Level Description.

  		3.1.1	Operational Description.
  		3.1.2	Structural Description.

  3.2

  Exemplary Embodiments.

  3.2.1

  First Embodiment: Frequency Modulation (FM) Mode.

  			3.2.1.1	Operational Description.
  			3.2.1.2	Structural Description.

  3.2.2

  Second Embodiment: Phase Modulation (PM) Mode.

  			3.2.2.1	Operational Description.
  			3.2.2.2	Structural Description.

  3.2.3

  Third Embodiment: Amplitude Modulation (AM) Mode.

  			3.2.3.1	Operational Description.
  			3.2.3.2	Structural Description.

  		3.2.4	Fourth Embodiment: In-phase/Quadrature-phase (“I/Q”)
  			Modulation Mode.

  			3.2.4.1	Operational Description.
  			3.2.4.2	Structural Description.

  3.2.5

  Other Embodiments.

  3.2.5.1

  Combination of Modulation Techniques

  3.3

  Methods and Systems for Implementing the Embodiments.

  3.3.1

  The Voltage Controlled Oscillator (FM Mode).

  			3.3.1.1	Operational Description.
  			3.3.1.2	Structural Description.

  3.3.2

  The Local Oscillator (PM, AM, and “I/Q” Modes).

  			3.3.2.1	Operational Description.
  			3.3.2.2	Structural Description.

  3.3.3

  The Phase Shifter (PM Mode).

  			3.3.3.1	Operational Description.
  			3.3.3.2	Structural Description.

  3.3.4

  The Phase Modulator (PM and “I/Q” Modes).

  			3.3.4.1	Operational Description.
  			3.3.4.2	Structural Description.

  3.3.5

  The Summing Module (AM Mode).

  			3.3.5.1	Operational Description.
  			3.3.5.2	Structural Description.

  3.3.6

  The Switch Module (FM, PM, and “I/Q” Modes).

  			3.3.6.1	Operational Description.
  			3.3.6.2	Structural Description.

  3.3.7

  The Switch Module (AM Mode).

  			3.3.7.1	Operational Description.
  			3.3.7.2	Structural Description.

  3.3.8

  The Summer (“I/Q” Mode).

  			3.3.8.1	Operational Description.
  			3.3.8.2	Structural Description.

  3.3.9

  The Filter (FM, PM, AM, and “I/Q” Modes).

  			3.3.9.1	Operational Description.
  			3.3.9.2	Structural Description.

  3.3.10

  The Transmission Module (FM, PM, AM, and “I/Q” Modes).

  			3.3.10.1	Operational Description.
  			3.3.10.2	Structural Description.

  3.3.11

  Other Implementations.

  4.	Harmonic Enhancement.

  4.1

  High Level Description.

  		4.1.1	Operational Description.
  		4.1.2	Structural Description.

  4.2

  Exemplary Embodiments.

  		4.2.1	First Embodiment: When a Square Wave Feeds the
  			Harmonic Enhancement Module to Create One Pulse per Cycle.

  			4.2.1.1	Operational Description.
  			4.2.1.2	Structural Description.

  		4.2.2	Second Embodiment: When a Square Wave Feeds the
  			Harmonic Enhancement Module to Create Two Pulses per Cycle.

  			4.2.2.1	Operational Description.
  			4.2.2.2	Structural Description.

  		4.2.3	Third Embodiment: When Any Waveform Feeds the
  			Harmonic Enhancement Module.

  			4.2.3.1	Operational Description.
  			4.2.3.2	Structural Description.

  4.2.4

  Other Embodiments.

  4.3

  Implementation Examples.

  		4.3.1	First Digital Logic Circuit.
  		4.3.2	Second Digital Logic Circuit.
  		4.3.3	Analog Circuit.
  		4.3.4	Other Implementations.

  4.3.4.1

  Multiple apertures.

  5.	Amplifier Module.

  5.1

  High Level Description.

  		5.1.1	Operational Description.
  		5.1.2	Structural Description.

  5.2

  Exemplary Embodiment.

  5.2.1

  Linear Amplifier.

  			5.2.1.1	Operational Description.
  			5.2.1.2	Structural Description.

  5.2.2

  Other Embodiments.

  5.3

  Implementation Examples.

  5.3.1

  Linear Amplifier.

  			5.3.1.1	Operational Description.
  			5.3.1.2	Structural Description.

  5.3.2

  Other Implementations.

  6.	Receiver/Transmitter System.

  	6.1	High Level Description.
  	6.2	Exemplary Embodiments and Implementation Examples.

  		6.2.1	First Embodiment: The Transmitter of the Present
  			Invention Being Used in a Circuit with a Superheterodyne Receiver.
  		6.2.2	Second Embodiment: The Transmitter of the Present
  			Invention Being Used with a Universal Frequency Down
  			Converter in a Half-Duplex Mode.
  		6.2.3	Third Embodiment: The Transmitter of the Present
  			Invention Being Used with a Universal Frequency Down
  			Converter in a Full-Duplex Mode.
  		6.2.4	Other Embodiments and Implementations.

  	6.3	Summary Description of Down-conversion Using a Universal
  		Frequency Translation Module.

  7.	Designing a Transmitter According to an Embodiment of the Present Invention.

  	7.1	Frequency of the Transmission Signal.
  	7.2	Characteristics of the Transmission Signal.
  	7.3	Modulation Scheme.
  	7.4	Characteristics of the Information Signal.
  	7.5	Characteristic of the Oscillating Signal.

  		7.5.1	Frequency of the Oscillating Signal.
  		7.5.2	Pulse Width of the String of Pulses.

  	7.6	Design of the Pulse Shaping Circuit.
  	7.7	Selection of the Switch.

  		7.7.1	Optimized Switch Structures.
  		7.7.2	Phased D2D - Splitter in CMOS

  	7.8	Design of the Filter.
  	7.9	Selection of an Amplifier.
  	7.10	Design of the Transmission Module.

  
  1. Terminology.
• Various terms used in this application are generally described in this section. Each description in this section is provided for illustrative and convenience purposes only, and is not limiting. The meaning of these terms will be apparent to persons skilled in the relevant art(s) based on the entirety of the teachings provided herein.
• Amplitude Modulation (AM): A modulation technique wherein the amplitude of the carrier signal is shifted (i.e., varied) as a function of the information signal. The frequency of the carrier signal typically remains constant. A subset of AM is referred to as “amplitude shift keying” which is used primarily for digital communications where the amplitude of the carrier signal shifts between discrete states rather than varying continuously as it does for analog information.
• Analog signal: A signal in which the information contained therein is continuous as contrasted to discrete, and represents a time varying physical event or quantity. The information content is conveyed by varying at least one characteristic of the signal, such as but not limited to amplitude, frequency, or phase, or any combinations thereof.
• Baseband signal: Any generic information signal desired for transmission and/or reception. As used herein, it refers to both the information signal that is generated at a source prior to any transmission (also referred to as the modulating baseband signal), and to the signal that is to be used by the recipient after transmission (also referred to as the demodulated baseband signal).
• Carrier signal: A signal capable of carrying information. Typically, it is an electromagnetic signal that can be varied through a process called modulation. The frequency of the carrier signal is referred to as the carrier frequency. A communications system may have multiple carrier signals at different carrier frequencies.
• Control a switch: Causing a switch to open and close. The switch may be, without limitation, mechanical, electrical, electronic, optical, etc., or any combination thereof. Typically, it is controlled by an electrical or electronic input. If the switch is controlled by an electronic signal, it is typically a different signal than the signals connected to either terminal of the switch.
• Demodulated baseband signal: The baseband signal that is to be used by the recipient after transmission. Typically it has been down converted from a carrier signal and has been demodulated. The demodulated baseband signal should closely approximate the information signal (i.e., the modulating baseband signal) in frequency, amplitude, and information.
• Demodulation: The process of removing information from a carrier or intermediate frequency signal.
• Digital signal: A signal in which the information contained therein has discrete states as contrasted to a signal that has a property that may be continuously variable.
• Direct down conversion: A down conversion technique wherein a received signal is directly down converted and demodulated, if applicable, from the original transmitted frequency (i.e., a carrier frequency) to baseband without having an intermediate frequency.
• Down conversion: A process for performing frequency translation in which the final frequency is lower than the initial frequency.
• Drive a switch: Same as control a switch.
• Frequency Modulation (FM): A modulation technique wherein the frequency of the carrier signal is shifted (i.e., varied) as a function of the information signal. A subset of FM is referred to as “frequency shift keying” which is used primarily for digital communications where the frequency of the carrier signal shifts between discrete states rather than varying continuously as it does for analog information.
• Harmonic: A harmonic is a frequency or tone that, when compared to its fundamental or reference frequency or tone, is an integer multiple of it. In other words, if a periodic waveform has a fundamental frequency of “f” (also called the first harmonic), then its harmonics may be located at frequencies of “n·f,” where “n” is 2, 3, 4, etc. The harmonic corresponding to n=2 is referred to as the second harmonic, the harmonic corresponding to n=3 is referred to as the third harmonic, and so on.
• In-phase (“I”) signal: The signal typically generated by an oscillator. It has not had its phase shifted and is often represented as a sine wave to distinguish it from a “Q” signal. The “I” signal can, itself, be modulated by any means. When the “I” signal is combined with a “Q” signal, the resultant signal is referred to as an “I/Q” signal.
• In-phase/Quadrature-phase (“I/Q”) signal: The signal that results when an “I” signal is summed with a “Q” signal. Typically, both the “I” and “Q” signals have been phase modulated, although other modulation techniques may also be used, such as amplitude modulation. An “I/Q” signal is used to transmit separate streams of information simultaneously on a single transmitted carrier. Note that the modulated “I” signal and the modulated “Q” signal are both carrier signals having the same frequency. When combined, the resultant “I/Q” signal is also a carrier signal at the same frequency.
• Information signal: The signal that contains the information that is to be transmitted. As used herein, it refers to the original baseband signal at the source. When it is intended that the information signal modulate a carrier signal, it is also referred to as the “modulating baseband signal.” It may be voice or data, analog or digital, or any other signal or combination thereof.
• Intermediate frequency (IF) signal: A signal that is at a frequency between the frequency of the baseband signal and the frequency of the transmitted signal.
• Modulation: The process of varying one or more physical characteristics of a signal to represent the information to be transmitted. Three commonly used modulation techniques are frequency modulation, phase modulation, and amplitude modulation. There are also variations, subsets, and combinations of these three techniques.
• Operate a switch: Same as control a switch.
• Phase Modulation (PM): A modulation technique wherein the phase of the carrier signal is shifted (i.e., varied) as a function of the information signal. A subset of PM is referred to as “phase shift keying” which is used primarily for digital communications where the phase of the carrier signal shifts between discrete states rather than varying continuously as it does for analog information.
• Quadrature-phase (“Q”) signal: A signal that is out of phase with an in-phase (“I”) signal. The amount of phase shift is predetermined for a particular application, but in a typical implementation, the “Q” signal is 90° out of phase with the “I” signal. Thus, if the “I” signal were a sine wave, the “Q” signal would be a cosine wave. When discussed together, the “I” signal and the “Q” signal have the same frequencies.
• Spectrum: Spectrum is used to signify a continuous range of frequencies, usually wide, within which electromagnetic (EM) waves have some specific common characteristic. Such waves may be propagated in any communication medium, both natural and manmade, including but not limited to air, space, wire, cable, liquid, waveguide, microstrip, stripline, optical fiber, etc. The EM spectrum includes all frequencies greater than zero hertz.
• Subharmonic: A subharmonic is a frequency or tone that is an integer submultiple of a referenced fundamental frequency or tone. That is, a subharmonic frequency is the quotient obtained by dividing the fundamental frequency by an integer. For example, if a periodic waveform has a frequency of “f” (also called the “fundamental frequency” or first subharmonic), then its subharmonics have frequencies of “f/n,” where n is 2, 3, 4, etc. The subharmonic corresponding to n=2 is referred to as the second subharmonic, the subharmonic corresponding to n=3 is referred to as the third subharmonic, and so on. A subharmonic itself has possible harmonics, and the i^thharmonic of the ith subharmonic will be at the fundamental frequency of the original periodic waveform. For example, the third subharmonic (which has a frequency of “f/3”) may have harmonics at integer multiples of itself (i.e., a second harmonic at “2·f/3,” a third harmonic at “3·f/3,” and so on). The third harmonic of the third subharmonic of the original signal (i.e., “3·f/3”) is at the frequency of the original signal.
• Trigger a switch: Same as control a switch.
• Up conversion: A process for performing frequency translation in which the final frequency is higher than the initial frequency.
• 2. Overview of the Invention.
• The present invention is directed to systems and methods for frequency up-conversion, and applications thereof.
• In one embodiment, the frequency up-converter of the present invention is used as a stable reference frequency source in a phase comparator or in a frequency comparator. This embodiment of the present invention achieves this through the use of a stable, low frequency local oscillator, a switch, and a filter. Because it up-converts frequency, the present invention can take advantage of the relatively low cost of low frequency oscillators to generate stable, high frequency signals.
• In a second embodiment, the frequency up-converter is used as a system and method for transmitting an electromagnetic (EM) signal.
• Based on the discussion contained herein, one skilled in the relevant art(s) will recognize that there are other, alternative embodiments in which the frequency up-converter of the present invention could be used in other applications, and that these alternative embodiments fall within the scope of the present invention.
• For illustrative purposes, various modulation examples are discussed below. However, it should be understood that the invention is not limited by these examples. Other modulation techniques that might be used with the present invention will be apparent to persons skilled in the relevant art(s) based on the teaching contained herein.
• Also for illustrative purposes, frequency up-conversion according to the present invention is described below in the context of a transmitter. However, the invention is not limited to this embodiment. Equivalents, extensions, variations, deviations, etc., of the following will be apparent to persons skilled in the relevant art(s) based on the teachings contained herein. Such equivalents, extensions, variations, deviations, etc., are within the scope and spirit of the present invention.
• 2.1 Discussion of Modulation Techniques.
• Techniques by which information can be imparted onto EM signals to be transmitted are called modulation. These techniques are generally well known to one skilled in the relevant art(s), and include, but are not limited to, frequency modulation (FM), phase modulation (PM), amplitude modulation (AM), quadrature-phase shift keying (QPSK), frequency shift keying (FSK), phase shift keying (PSK), amplitude shift keying (ASK), etc., and combinations thereof. These last three modulation techniques, FSK, PSK, and ASK, are subsets of FM, PM, and AM, respectively, and refer to circuits having discrete input signals (e.g., digital input signals).
• For illustrative purposes only, the circuits and techniques described below all refer to the EM broadcast medium. However, the invention is not limited by this embodiment. Persons skilled in the relevant art(s) will recognize that these same circuits and techniques can be used in all transmission media (e.g., over-the-air broadcast, point-to-point cable, etc.).
• 2.2 Explanation of Exemplary Circuits and Waveforms.
• 2.2.1 Frequency Modulation.
• FIG. 1 illustrates an example of a frequency modulation (FM)circuit100 andFIGS. 2A, 2B, and2C, andFIGS. 20A, 20B, and20C illustrate examples of waveforms at several points inFM circuit100. In an FM system, the frequency of a carrier signal, such as an oscillating signal202 (FIG. 2B andFIG. 20B), is varied to represent the data to be communicated, such as information signals102 ofFIGS. 2A and 2002 ofFIG. 20A. InFIG. 20A,information signal2002 is a continuous signal (i.e., an analog signal), and inFIG. 2A, information signal102 is a discrete signal (i.e., a digital signal). In the case of thediscrete information signal102, theFM circuit100 is referred to as a frequency shift keying (FSK) system, which is a subset of an FM system.
• Frequency modulation circuit100 receives aninformation signal102,2002 from a source (not shown).Information signal102,2002 can be amplified by anoptional amplifier104 and filtered by anoptional filter114 and is the voltage input that drives a voltage controlled oscillator (VCO)106. WithinVCO106, an oscillating signal202 (seen onFIG. 2B andFIG. 20B) is generated. The purpose ofVCO106 is to vary the frequency ofoscillating signal202 as a function of the input voltage, i.e., information signal102,2002. The output ofVCO106 is a modulated signal shown as modulated signal108 (FIG. 2C) when the information signal is thedigital information signal102 and shown as modulated signal2004 (FIG. 20C) when the information signal is theanalog signal2002.Modulated signal108,2004 is at a relatively low frequency (e.g., generally between 50 MHz and 100 MHz) and can have its frequency increased by an optional frequency multiplier110 (e.g., to 900 MHz, 1.8 GHz) and have its amplitude increased by anoptional amplifier116. The output ofoptional frequency multiplier110 and/oroptional amplifier116 is then transmitted by anexemplary antenna112.
• 2.2.2 Phase Modulation.
• FIG. 3 illustrates an example of a phase modulation (PM)circuit300 andFIGS. 4A, 4B, and4C, andFIGS. 21A, 21B, and21C illustrate examples of waveforms at several points inPM circuit300. In a PM system, the phase of a carrier signal, such as a local oscillator (LO) output308 (FIG. 4B andFIG. 21B), is varied to represent the data to be communicated, such as an information signals302 ofFIGS. 4A and 2102 ofFIG. 21A. InFIG. 21A,information signal2102 is a continuous signal (i.e., an analog signal), and inFIG. 4A, information signal302 is a discrete signal (i.e., a digital signal). In the case of thediscrete information signal302, the PM circuit is referred to as a phase shift keying (PSK) system. This is the typical implementation, and is a subset of a PM system.
• Phase modulation circuit300 receivesinformation signal302,2102 from a source (not shown).Information signal302,2102 can be amplified by anoptional amplifier304 and filtered by anoptional filter318 and is routed to aphase modulator306. Also feedingphase modulator306 isLO output308 of alocal oscillator310.LO output308 is shown onFIG. 4B andFIG. 21B. Local oscillators, such aslocal oscillator310, output an electromagnetic wave at a predetermined frequency and amplitude.
• The output ofphase modulator306 is a modulated signal shown as a phase modulated signal312 (FIG. 4C) when the information signal is the discrete information signal302 and shown as a phase modulated signal2104 (FIG. 21C) when the information signal is theanalog information signal2102. The purpose ofphase modulator306 is to change the phase ofLO output308 as a function of the value ofinformation signal302,2102. That is, for example in a PSK mode, ifLO output308 were a sine wave, and the value of information signal302 changed from a binary high to a binary low, the phase ofLO output308 would change from a sine wave with a zero phase to a sine wave with, for example, a phase of 180°. The result of this phase change would be phase modulatedsignal312 ofFIG. 4C which would have the same frequency asLO output308, but would be out of phase by 180° in this example. For a PSK system, the phase changes in phase modulatedsignal312 that are representative of the information in information signal302 can be seen by comparingwaveforms302,308, and312 onFIGS. 4A, 4B, and4C. For the case of ananalog information signal2102 ofFIG. 21A, the phase ofLO output308 ofFIG. 21B changes continuously as a function of the amplitude of theinformation signal2102. That is, for example, asinformation signal2102 increases from a value of “X” to “X+δx”, thePM signal2104 ofFIG. 21C changes from a signal which may be represented by the equation sin(ωt) to a signal which can be represented by the equation sin(ωt+φ), where φ is the phase change associated with a change of δx ininformation signal2102. For an analog PM system, the phase changes in phase modulatedsignal2104 that are representative of the information ininformation signal2102 can be seen by comparingwaveforms2102,308, and2104 onFIGS. 21A, 21B, and21C.
• Afterinformation signal302,2102 andLO output308 have been modulated byphase modulator306, phase modulatedsignal312,2104 can be routed to anoptional frequency multiplier314 andoptional amplifier320. The purpose ofoptional frequency multiplier314 is to increase the frequency of phase modulatedsignal312 from a relatively low frequency (e.g., 50 MHz to 100 MHz) to a desired broadcast frequency (e.g., 900 MHz, 1.8 GHz).Optional amplifier320 raises the signal strength of phase modulatedsignal312,2104 to a desired level to be transmitted by anexemplary antenna316.
• 2.2.3 Amplitude Modulation.
• FIG. 5 illustrates an example of an amplitude modulation (AM)circuit500 andFIGS. 6A, 6B, and6C, andFIGS. 22A, 22B, and22C illustrate examples of waveforms at several points inAM circuit500. In an AM system, the amplitude of a carrier signal, such as a local oscillator (LO) signal508 (FIG. 6B andFIG. 22B), is varied to represent the data to be communicated, such as information signals502 ofFIGS. 6A and 2202 ofFIG. 22A. InFIG. 22A,information signal2202 is a continuous signal (i.e., an analog signal), and inFIG. 6A, information signal502 is a discrete signal (i.e., a digital signal). In the case of thediscrete information signal502, the AM circuit is referred to as an amplitude shift keying (ASK) system, which is a subset of an AM system.
• Amplitude modulation circuit500 receives information signal502 from a source (not shown).Information signal502,2202 can be amplified by anoptional amplifier504 and filtered by anoptional filter518.Amplitude modulation circuit500 also includes a local oscillator (LO)506 which has anLO output508.Information signal502,2202 andLO output508 are then multiplied by amultiplier510. The purpose ofmultiplier510 is to cause the amplitude ofLO output508 to vary as a function of the amplitude ofinformation signal502,2202. The output ofmultiplier510 is a modulated signal shown as amplitude modulated signal512 (FIG. 6C) when the information signal is thedigital information signal502 and shown as modulated signal2204 (FIG. 22C) when the information signal is theanalog information signal2202.AM signal512,2204 can then be routed to anoptional frequency multiplier514 where the frequency ofAM signal512,2204 is increased from a relatively low level (e.g., 50 MHz to 100 MHz) to a higher level desired for broadcast (e.g., 900 MHz, 1.8 GHz) and anoptional amplifier520, which increases the signal strength ofAM signal512,2204 to a desired level for broadcast by anexemplary antenna516.
• 2.2.4 In-Phase/Quadrature-Phase Modulation.
• FIG. 7 illustrates an example of an in-phase/quadrature-phase (“I/Q”)modulation circuit700 andFIGS. 8A, 8B,8C,8D, and8E illustrate examples of waveforms at several points in “I/Q”modulation circuit700. In this technique, which increases bandwidth efficiency, separate information signals can be simultaneously transmitted on carrier signals that are out of phase with each other. That is, a first information signal702 ofFIG. 8A can be modulated onto the in-phase (“I”)oscillator signal710 ofFIG. 8B and a second information signal704 ofFIG. 8C can be modulated onto the quadrature-phase (“Q”)oscillator signal712 ofFIG. 8D. The “I” modulated signal is combined with the “Q” modulated signal and the resulting “I/Q” modulated signal is then transmitted. In a typical usage, both information signals are digital, and both are phase modulated onto the “I” and “Q” oscillating signals. One skilled in the relevant art(s) will recognize that the “I/Q” mode can also work with analog information signals, with combinations of analog and digital signals, with other modulation techniques, or any combinations thereof.
• This “I/Q” modulation system uses two PM circuits together in order to increase the bandwidth efficiency. As stated above, in a PM circuit, the phase of an oscillating signal, such as710 (or712) (FIG. 8B or8D), is varied to represent the data to be communicated, such as an information signal such as702 (or704). For ease of understanding and display, the discussion herein will describe the more typical use of the “I/Q” mode, that is, with digital information signals and phase modulation on both oscillating signals. Thus, both signal streams are phase shift keying (PSK), which is a subset of PM.
• “I/Q”modulation circuit700 receives aninformation signal702 from a first source (not shown) and aninformation signal704 from a second source (not shown). Examples of information signals702 and704 are shown inFIGS. 8A and 8C. Information signals702 and704 can be amplified byoptional amplifiers714 and716 and filtered byoptional filters734 and736. It is then routed to phasemodulators718 and720. Also feedingphase modulators718 and720 are oscillatingsignals710 and712.Oscillating signal710 was generated by alocal oscillator706, and is shown inFIG. 8B, andoscillating signal712 is the phase shifted output oflocal oscillator706. Local oscillators, such aslocal oscillator706, output an electromagnetic wave at a predetermined frequency and amplitude.
• The output ofphase modulator718 is a phase modulatedsignal722 which is shown using a dotted line as one of the waveforms inFIG. 8E. Similarly, the output ofphase modulator720, which operates in a manner similar tophase modulator718, is a phase modulatedsignal724 which is shown using a solid line as the other waveform inFIG. 8E. The effect ofphase modulators718 and720 on oscillatingsignals710 and712 is to cause them to change phase. As stated above, the system shown here is a PSK system, and as such, the phase of oscillatingsignals710 and712 is shifted byphase modulators718 and720 by a discrete amount as a function of information signals702 and704.
• For simplicity of discussion and ease of display, oscillatingsignal710 is shown onFIG. 8B as a sine wave and is referred to as the “I” signal in the “I/Q”circuit700. After the output ofoscillator706 has gone through a phase shifter708, shown here as shifting the phase by −π/2, oscillatingsignal712 is a cosine wave, shown onFIG. 8D, and is referred to as the “Q” signal in the “I/Q” circuit. Again, for ease of display,phase modulators718 and720 are shown as shifting the phase of the respectiveoscillating signals710 and712 by 180°. This is seen onFIG. 8E.Modulated signal722 is summed with modulatedsignal724 by asummer726. The output ofsummer726 is the arithmetic sum of modulatedsignal722 and724 and is an “I/Q”signal728. (For clarity of the display onFIG. 8E, the combinedsignal728 is not shown. However, one skilled in the relevant art(s) will recognize that the arithmetic sum of 2 sinusoidal waves having the same frequency is also a sinusoidal wave at that frequency.)
• “I/Q”signal728 can then be routed to anoptional frequency multiplier730, where the frequency of “I/Q”signal718 is increased from a relatively low level (e.g., 50 MHz to 100 MHz) to a higher level desired for broadcast (e.g., 900 MHz, 1.8 GHz), and to anoptional amplifier738 which increases the signal strength of “I/Q”signal728 to a desired level for broadcast by anexemplary antenna732.
• 2.3 Features of the Invention.
• As apparent from the above, several frequencies are involved in a communications system. The frequency of the information signal is relatively low. The frequency of the local oscillator (both the voltage controlled oscillator as well as the other oscillators) is higher than that of the information signal, but typically not high enough for efficient transmission. A third frequency, not specifically mentioned above, is the frequency of the transmitted signal which is greater than or equal to the frequency of the oscillating signal. This is the frequency that is routed from the optional frequency multipliers and optional amplifiers to the antennas in the previously described circuits.
• Typically, in the transmitter subsystem of a communications system, upconverting the information signal to broadcast frequency requires, at least, filters, amplifiers, and frequency multipliers. Each of these components is costly, not only in terms of the purchase price of the component, but also because of the power required to operate them.
• The present invention provides a more efficient means for producing a modulated carrier for transmission, uses less power, and requires fewer components. These and additional advantages of the present invention will be apparent from the following description.
• 3. Frequency Up-conversion.
• The present invention is directed to systems and methods for frequency up-conversion and applications of the same. In one embodiment, the frequency up-converter of the present invention allows the use of a stable, low frequency oscillator to generate a stable high frequency signal that, for example and without limitation, can be used as a reference signal in a phase comparator or a frequency comparator. In another embodiment, the up-converter of the present invention is used in a transmitter. The invention is also directed to a transmitter. Based on the discussion contained herein, one skilled in the relevant art(s) will recognize that there are other, alternative embodiments and applications in which the frequency up-converter of the present invention could be used, and that these alternative embodiments and applications fall within the scope of the present invention.
• For illustrative purposes, frequency up-conversion according to the present invention is described below in the context of a transmitter. However, as apparent from the preceding paragraph, the invention is not limited to this embodiment.
• The following sections describe methods related to a transmitter and frequency up-converter. Structural exemplary embodiments for achieving these methods are also described. It should be understood that the invention is not limited to the particular embodiments described below. Equivalents, extensions, variations, deviations, etc., of the following will be apparent to persons skilled in the relevant art(s) based on the teachings contained herein. Such equivalents, extensions, variations, deviations, etc., are within the scope and spirit of the present invention.
• 3.1. High Level Description.
• This section (including its subsections) provides a high-level description of up-converting and transmitting signals according to the present invention. In particular, an operational process of frequency up-conversion in the context of transmitting signals is described at a high-level. The operational process is often represented by flowcharts. The flowcharts are presented herein for illustrative purposes only, and are not limiting. In particular, the use of flowcharts should not be interpreted as limiting the invention to discrete or digital operation. In practice, those skilled in the relevant art(s) will appreciate, based on the teachings contained herein, that the invention can be achieved via discrete operation, continuous operation, or any combination thereof. Furthermore, the flow of control represented by the flowcharts is also provided for illustrative purposes only, and it will be appreciated by persons skilled in the relevant art(s) that other operational control flows are within the scope and spirit of the invention.
• Also, a structural implementation for achieving this process is described at a high-level. This structural implementation is described herein for illustrative purposes, and is not limiting. In particular, the process described in this section can be achieved using any number of structural implementations, one of which is described in this section. The details of such structural implementations will be apparent to persons skilled in the relevant art(s) based on the teachings contained herein.
• 3.1.1 Operational Description.
• Theflow chart900 ofFIG. 9 demonstrates the operational method of frequency up-conversion in the context of transmitting a signal according to an embodiment of the present invention. The invention is directed to both frequency up-conversion and transmitting signals as represented inFIG. 9. Representative waveforms for signals generated inflow chart900 are depicted inFIG. 19. For purposes of illustrating the high level operation of the invention, frequency modulation of a digital information signal is depicted. The invention is not limited to this exemplary embodiment. One skilled in the relevant art(s) will appreciate that other modulation modes could alternatively be used (as described in later sections).
• Instep902, an information signal1902 (FIG. 19A) is generated by a source. This information signal may be analog, digital, and any combination thereof, or anything else that is desired to be transmitted, and is at the baseband frequency. As described below, theinformation signal1902 is used to modulate anintermediate signal1904. Accordingly, theinformation signal1902 is also herein called a modulating baseband information signal. In the example ofFIG. 19A, theinformation signal1902 is illustrated as a digital signal. However, the invention is not limited to this embodiment. As noted above, theinformation signal1902 can be analog, digital, and/or any combination thereof.
• An oscillating signal1904 (FIG. 19B) is generated instep904. Instep906, theoscillating signal1904 is modulated, where the modulation is a result of, and a function of, theinformation signal1902. Step906 produces a modulated oscillating signal1906 (FIG. 19C), also called a modulated intermediate signal. As noted above, the flowchart ofFIG. 9 is being described in the context of an example where theinformation signal1902 is a digital signal. However, alternatively, theinformation signal1902 can be analog or any combination of analog and digital. Also, the example shown inFIG. 19 uses frequency shift keying (FSK) as the modulation technique. Alternatively, any modulation technique (e.g., FM, AM, PM, ASK, PSK, etc., or any combination thereof) can be used. The remaining steps908-912 of the flowchart ofFIG. 9 operate in the same way, whether theinformation signal1902 is digital, analog, etc., or any combination thereof, and regardless of what modulation technique is used.
• A harmonically rich signal1908 (FIG. 19D) is generated from the modulatedsignal1906 instep908.Signal1908 has a substantially continuous and periodically repeated waveform. In an embodiment, the waveform ofsignal1908 is substantially rectangular, as is seen in the expandedwaveform1910 ofFIG. 19E. One skilled in the relevant art(s) will recognize the physical limitations to and mathematical obstacles against achieving an exact or perfect rectangular waveform and it is not the intent or requirement of the present invention that a perfect rectangular waveform be generated or needed. However, for ease of discussion, the term “rectangular waveform” will be used herein and will refer to waveforms that are substantially rectangular, and will include but will not be limited to those waveforms that are generally referred to as square waves or pulses. It should be noted that if the situation arises wherein a perfect rectangular waveform is proven to be both technically and mathematically feasible, that situation will also fall within the scope and intent of this invention A continuous periodic waveform (such as waveform1908) is composed of a series of sinusoidal waves of specific amplitudes and phases, the frequencies of which are integer multiples of the repetition frequency of the waveform. (A waveform's repetition frequency is the number of times per second the periodic waveform repeats.) A portion of the waveform ofsignal1908 is shown in an expanded view aswaveform1910 ofFIG. 19E. The first three sinusoidal components of waveform1910 (FIG. 19E) are depicted aswaveforms1912a, b, &cofFIG. 19F andwaveforms1914a, b, &cofFIG. 19G. (In the examples ofFIGS. 19F & G, the three sinusoidal components are shown separately. In actuality, these waveforms, along with all the other sinusoidal components which are not shown, occur simultaneously, as seen inFIG. 19H. Note that inFIG. 19H, the waveforms are shown simultaneously, but are not shown summed. Ifwaveforms1912 and1914 were shown summed, they would, in the limit, i.e., with an infinite number of sinusoidal components, be identical to theperiodic waveform1910 ofFIG. 19E. For ease of illustration, only the first three of the infinite number of sinusoidal components are shown.) These sinusoidal waves are called harmonics, and their existence can be demonstrated both graphically and mathematically. Each harmonic (waveforms1912a, b, &cand1914a, b, &c) has the same information content as does waveform1910 (which has the same information as the corresponding portion of waveform1908). Accordingly, the information content ofwaveform1908 can be obtained from any of its harmonics. As the harmonics have frequencies that are integer multiples of the repetition frequency ofsignal1908, and since they have the same information content as signal1908 (as just stated), the harmonics each represent an up-converted representation ofsignal1908. Some of the harmonics are at desired frequencies (such as the frequencies desired to be transmitted). These harmonics are called “desired harmonics” or “wanted harmonics.” According to the invention, desired harmonics have sufficient amplitude for accomplishing the desired processing (i.e., being transmitted). Other harmonics are not at the desired frequencies. These harmonics are called “undesired harmonics” or “unwanted harmonics.”
• Instep910, any unwanted harmonics of the continuous periodic waveform ofsignal1908 are filtered out (for example, any harmonics that are not at frequencies desired to be transmitted). In the example ofFIG. 19, the first and second harmonics (i.e., those depicted bywaveforms1912a&bofFIGS. 19F and 1914a&bofFIG. 19G) are the unwanted harmonics. Instep912, the remaining harmonic, in the example ofFIG. 19, the third harmonic (i.e., those depicted bywaveforms1912cofFIGS. 19F and 1914cofFIG. 19G), is transmitted. This is depicted by waveform1918 ofFIG. 19I. In the example ofFIG. 19, only three harmonics are shown, and the lowest two are filtered out to leave the third harmonic as the desired harmonic. In actual practice, there are an infinite number of harmonics, and the filtering can be made to remove unwanted harmonics that are both lower in frequency than the desired harmonic as well as those that are higher in frequency than the desired harmonic.
• 3.1.2 Structural Description.
• FIG. 10 is a block diagram of an up-conversion system according to an embodiment of the invention. This embodiment of the up-conversion system is shown as atransmitter1000.Transmitter1000 includes anacceptance module1004, a harmonic generation andextraction module1006, and atransmission module1008 that accepts aninformation signal1002 and outputs a transmittedsignal1014.
• Preferably, theacceptance module1004, harmonic generation andextraction module1006, andtransmission module1008 process the information signal in the manner shown in theoperational flowchart900. In other words,transmitter1000 is the structural embodiment for performing the operational steps offlowchart900. However, it should be understood that the scope and spirit of the present invention includes other structural embodiments for performing the steps offlowchart900. The specifics of these other structural embodiments will be apparent to persons skilled in the relevant art(s) based on the discussion contained herein.
• The operation of thetransmitter1000 will now be described in detail with reference to theflowchart900. Instep902, an information signal1002 (for example, seeFIG. 19A) from a source (not shown) is routed toacceptance module1004. Instep904, an oscillating signal (for example, seeFIG. 19B) is generated and instep906, it is modulated, thereby producing a modulated signal1010 (for an example of FM, seeFIG. 19C). The oscillating signal can be modulated using any modulation technique, examples of which are described below. Instep908, the harmonic generation and extraction module (HGEM) generates a harmonically rich signal with a continuous and periodic waveform (an example of FM can be seen inFIG. 19D). This waveform is preferably a rectangular wave, such as a square wave or a pulse (although, the invention is not limited to this embodiment), and is comprised of a plurality of sinusoidal waves whose frequencies are integer multiples of the fundamental frequency of the waveform. These sinusoidal waves are referred to as the harmonics of the underlying waveform. A Fourier series analysis can be used to determine the amplitude of each harmonic (for example, seeFIGS. 19F and 19G). Instep910, a filter (not shown) withinHGEM1006 filters out the undesired frequencies (harmonics), and outputs an electromagnetic (EM) signal1012 at the desired frequency (for example, seeFIG. 191). Instep912,EM signal1012 is routed to transmission module1008 (optional), where it is prepared for transmission. Thetransmission module1008 then outputs a transmittedsignal1014.
• 3.2 Exemplary Embodiments.
• Various embodiments related to the method(s) and structure(s) described above are presented in this section (and its subsections). These embodiments are described herein for purposes of illustration, and not limitation. The invention is not limited to these embodiments. Alternate embodiments (including equivalents, extensions, variations, deviations, etc., of the embodiments described herein) will be apparent to persons skilled in the relevant art(s) based on the teachings contained herein. The invention is intended and adapted to include such alternate embodiments.
• 3.2.1 First Embodiment: Frequency Modulation (FM) Mode.
• In this embodiment, an information signal is accepted and a modulated signal whose frequency varies as a function of the information signal results.
• 3.2.1.1 Operational Description.
• The flow chart ofFIG. 11 demonstrates the method of operation of a transmitter in the frequency modulation (FM) mode according to an embodiment of the present invention. As stated above, the representative waveforms shown inFIG. 19 depict the invention operating as a transmitter in the FM mode.
• Instep1102, an information signal1902 (FIG. 19A) is generated by a source by any means and/or process. (Information signal1902 is a baseband signal, and, because it is used to modulate a signal, may also be referred to as a modulatingbaseband signal1902.)Information signal1902 may be, for example, analog, digital, or any combination thereof. The signals shown inFIG. 19 depict a digital information signal wherein the information is represented by discrete states of the signal. It will be apparent to persons skilled in the relevant art(s) that the invention is also adapted to working with an analog information signal wherein the information is represented by a continuously varying signal. Instep1104,information signal1902 modulates an oscillating signal1904 (FIG. 19B). The result of this modulation is the modulated signal1906 (FIG. 19C) as indicated inblock1106.Modulated signal1906 has a frequency that varies as a function ofinformation signal1902 and is referred to as an FM signal.
• Instep1108, a harmonically rich signal with a continuous periodic waveform, shown inFIG. 19D asrectangular waveform1908, is generated.Rectangular waveform1908 is generated using the modulatedsignal1906. One skilled in the relevant art(s) will recognize the physical limitations to and mathematical obstacles against achieving an exact or perfect rectangular waveform and it is not the intent of the present invention that a perfect rectangular waveform be generated or needed. Again, as stated above, for ease of discussion, the term “rectangular waveform” will be used to refer to waveforms that are substantially rectangular. In a similar manner, the term “square wave” will refer to those waveforms that are substantially square and it is not the intent of the present invention that a perfect square wave be generated or needed. A portion ofrectangular waveform1908 is shown in an expanded view asperiodic waveform1910 inFIG. 19E. The first part ofwaveform1910 is designated “signal A” and representsinformation signal1902 being “high,” and the second part ofwaveform1910 is designated “signal B” andinformation signal1902 being “low.” It should be noted that this convention is used for illustrative purposes only, and alternatively, other conventions could be used.
• As stated before, a continuous and periodic waveform, such as arectangular wave1908 as indicated inblock1110 offlowchart1100, has sinusoidal components (harmonics) at frequencies that are integer multiples of the fundamental frequency of the underlying waveform (i.e., at the Fourier component frequencies). Three harmonics ofperiodic waveform1910 are shown separately, in expanded views, inFIGS. 19F and 19G. Since waveform1910 (and also waveform1908) is shown as a square wave in this exemplary embodiment, only the odd harmonics are present, i.e., the first, third, fifth, seventh, etc. As shown inFIG. 19, ifrectangular waveform1908 has a fundamental frequency of f₁(also known as the first harmonic), the third harmonic will have a frequency of 3·f₁, the fifth harmonic will have a frequency of 5·f₁, and so on. The first, third, and fifth harmonics of signal A are shown aswaveforms1912a,1912b, and1912cofFIG. 19F, and the first, third, and fifth harmonics of signal B are shown aswaveforms1914a,1914b, and1914cofFIG. 19G. In actuality, these harmonics (as well as all of the higher order harmonics) occur simultaneously, as shown by waveform1916 ofFIG. 19H. Note that if all of the harmonic components ofFIG. 19H were shown summed together with all of the higher harmonics (i.e., the seventh, the ninth, etc.) the resulting waveform would, in the limit, be identical towaveform1910.
• Instep1112, the unwanted frequencies of waveform1916 are removed. In the example ofFIG. 19, the first and third harmonics are shown to be removed, and as indicated inblock1114, the remaining waveform1918 (i.e.,waveforms1912cand1914c) is at the desired EM frequency. Although not shown, the higher harmonics (e.g., the seventh, ninth, etc.) are also removed.
• The EM signal, shown here as remaining waveform1918, is prepared for transmission instep1116, and instep1118, the EM signal is transmitted.
• 3.2.1.2 Structural Description.
• FIG. 12 is a block diagram of a transmitter according to an embodiment of the invention. This embodiment of the transmitter is shown as an FM transmitter1200. FM transmitter1200 includes a voltage controlled oscillator (VCO)1204, aswitch module1214, afilter1218, and atransmission module1222 that accepts aninformation signal1202 and outputs a transmittedsignal1224. The operation and structure of exemplary components are described below: an exemplary VCO is described below at sections 3.3.1-3.3.1.2; an exemplary switch module is described below at sections 3.3.6-3.3.6.2; an exemplary filter is described below at sections 3.3.9-3.3.9.2; and an exemplary transmission module is described below at sections 3.3.10-3.3.10.2.
• Preferably, the voltage controlledoscillator1204,switch module1214,filter1218, andtransmission module1222 process the information signal in the manner shown in theoperational flowchart1100. In other words, FM transmitter1200 is the structural embodiment for performing the operational steps offlowchart1100. However, it should be understood that the scope and spirit of the present invention includes other structural embodiments for performing the steps offlowchart1100. The specifics of these other structural embodiments will be apparent to persons skilled in the relevant art(s) based on the discussion contained herein.
• The operation of the transmitter1200 will now be described in detail with reference to theflowchart1100. Instep1102, an information signal1202 (for example, seeFIG. 19A) from a source (not shown) is routed toVCO1204. Instep1104, an oscillating signal (for example, seeFIG. 19B) is generated and modulated, thereby producing a frequency modulated signal1210 (for example, seeFIG. 19C). Instep1108, theswitch module1214 generates a harmonicallyrich signal1216 with a continuous and periodic waveform (for example, seeFIG. 19D). This waveform is preferably a rectangular wave, such as a square wave or a pulse (although, the invention is not limited to this embodiment), and is comprised of a plurality of sinusoidal waves whose frequencies are integer multiples of the fundamental frequency of the waveform. These sinusoidal waves are referred to as the harmonics of the underlying waveform, and a Fourier analysis will determine the amplitude of each harmonic (for example, seeFIGS. 19F and 19G). Instep1112, afilter1218 filters out the undesired frequencies (harmonics), and outputs an electromagnetic (EM) signal1220 at the desired harmonic frequency (for example, seeFIG. 191). Instep1116,EM signal1220 is routed to transmission module1222 (optional), where it is prepared for transmission. Instep1118,transmission module1222 outputs a transmittedsignal1224.
• 3.2.2 Second Embodiment: Phase Modulation (PM) Mode.
• In this embodiment, an information signal is accepted and a modulated signal whose phase varies as a function of the information signal is transmitted.
• 3.2.2.1 Operational Description.
• The flow chart ofFIG. 13 demonstrates the method of operation of the transmitter in the phase modulation (PM) mode. The representative waveforms shown inFIG. 44 depict the invention operating as a transmitter in the PM mode.
• Instep1302, an information signal4402 (FIG. 44A) is generated by a source.Information signal4402 may be, for example, analog, digital, or any combination thereof. The signals shown inFIG. 44 depict a digital information signal wherein the information is represented by discrete states of the signal. It will be apparent to persons skilled in the relevant art(s) that the invention is also adapted to working with an analog information signal wherein the information is represented by a continuously varying signal. Instep1304, anoscillating signal4404 is generated and instep1306, the oscillating signal4404 (FIG. 44B) is modulated by theinformation signal4402, resulting in the modulated signal4406 (FIG. 44C) as indicated inblock1308. The phase of this modulatedsignal4406 is varied as a function of theinformation signal4402.
• A harmonically rich signal4408 (FIG. 44D) with a continuous periodic waveform is generated atstep1310 using modulatedsignal4406. Harmonicallyrich signal4408 is a substantially rectangular waveform. One skilled in the relevant art(s) will recognize the physical limitations to and mathematical obstacles against achieving an exact or perfect rectangular waveform and it is not the intent of the present invention that a perfect rectangular waveform be generated or needed. Again, as stated above, for ease of discussion, the term “rectangular waveform” will be used to refer to waveforms that are substantially rectangular. In a similar manner, the term “square wave” will refer to those waveforms that are substantially square and it is not the intent of the present invention that a perfect square wave be generated or needed. As stated before, a continuous and periodic waveform, such as the harmonicallyrich signal4408 as indicated inblock1312, has sinusoidal components (harmonics) at frequencies that are integer multiples of the fundamental frequency of the underlying waveform (the Fourier component frequencies). The first three harmonic waveforms are shown inFIGS. 44E, 44F, and44G. In actual fact, there are an infinite number of harmonics. Instep1314, the unwanted frequencies are removed, and as indicated inblock1316, the remaining frequency is at the desired EM output. As an example, the first (fundamental) harmonic4410 and the second harmonic4412 along with the fourth, fifth, etc., harmonics (not shown) might be filtered out, leaving the third harmonic4414 as the desired EM signal as indicated inblock1316.
• The EM signal is prepared for transmission instep1318, and instep1320, the EM signal is transmitted.
• 3.2.2.2 Structural Description.
• FIG. 14 is a block diagram of a transmitter according to an embodiment of the invention. This embodiment of the transmitter is shown as a PM transmitter1400. PM transmitter1400 includes alocal oscillator1406, aphase modulator1404, aswitch module1410, afilter1414, and atransmission module1418 that accepts aninformation signal1402 and outputs a transmittedsignal1420. The operation and structure of exemplary components are described below: an exemplary phase modulator is described below at sections 3.3.4-3.3.4.2; an exemplary local oscillator is described below at sections 3.3.2-3.3.2.2; an exemplary switch module is described below at sections 3.3.6-3.3.6.2; an exemplary filter is described below at sections 3.3.9-3.3.9.2; and an exemplary transmission module is described below at sections 3.3.10-3.3.10.2.
• Preferably, thelocal oscillator1406,phase modulator1404,switch module1410,filter1414, andtransmission module1418 process the information signal in the manner shown in theoperational flowchart1300. In other words, PM transmitter1400 is the structural embodiment for performing the operational steps offlowchart1300. However, it should be understood that the scope and spirit of the present invention includes other structural embodiments for performing the steps offlowchart1300. The specifics of these other structural embodiments will be apparent to persons skilled in the relevant art(s) based on the discussion contained herein.
• The operation of the transmitter1400 will now be described in detail with reference to theflowchart1300. Instep1302, an information signal1402 (for example, seeFIG. 44A) from a source (not shown) is routed tophase modulator1404. Instep1304, an oscillating signal from local oscillator1406 (for example, seeFIG. 44B) is generated and modulated, thereby producing a modulated signal1408 (for example, seeFIG. 44C). Instep1310, theswitch module1410 generates a harmonicallyrich signal1412 with a continuous and periodic waveform (for example, seeFIG. 44D). This waveform is preferably a rectangular wave, such as a square wave or a pulse (although, the invention is not limited to this embodiment), and is comprised of a plurality of sinusoidal waves whose frequencies are integer multiples of the fundamental frequency of the waveform. These sinusoidal waves are referred to as the harmonics of the underlying waveform, and a Fourier analysis will determine the amplitude of each harmonic (for an example of the first three harmonics, seeFIGS. 44E, 44F, and44G). Instep1314, afilter1414 filters out the undesired harmonic frequencies (for example, the first harmonic4410, the second harmonic4412, and the fourth, fifth, etc., harmonics, not shown), and outputs an electromagnetic (EM) signal1416 at the desired harmonic frequency (for example, the third harmonic, seeFIG. 44G). Instep1318,EM signal1416 is routed to transmission module1418 (optional), where it is prepared for transmission. Instep1320, thetransmission module1418 outputs a transmittedsignal1420.
• 3.2.3 Third Embodiment: Amplitude Modulation (AM) Mode.
• In this embodiment, an information signal is accepted and a modulated signal whose amplitude varies as a function of the information signal is transmitted.
• 3.2.3.1 Operational Description.
• The flow chart ofFIG. 15 demonstrates the method of operation of the transmitter in the amplitude modulation (AM) mode. The representative waveforms shown inFIG. 45 depict the invention operating as a transmitter in the AM mode.
• Instep1502, an information signal4502 (FIG. 45A) is generated by a source.Information signal4502 may be, for example, analog, digital, or any combination thereof. The signals shown inFIG. 45 depict a digital information signal wherein the information is represented by discrete states of the signal. It will be apparent to persons skilled in the relevant art(s) that the invention is also adapted to working with an analog information signal wherein the information is represented by a continuously varying signal. Instep1504, a “reference signal” is created, which, as indicated inblock1506, has an amplitude that is a function of theinformation signal4502. In one embodiment of the invention, the reference signal is created by combining theinformation signal4502 with a bias signal. In another embodiment of the invention, the reference signal is comprised of only theinformation signal4502. One skilled in the relevant art(s) will recognize that any number of embodiments exist wherein the reference signal will vary as a function of the information signal.
• An oscillating signal4504 (FIG. 45B) is generated atstep1508, and atstep1510, the reference signal (information signal4502) is gated at a frequency that is a function of theoscillating signal4504. The gated referenced signal is a harmonically rich signal4506 (FIG. 45C) with a continuous periodic waveform and is generated atstep1512. This harmonically rich signal4506 as indicated inblock1514 is substantially a rectangular wave which has a fundamental frequency equal to the frequency at which the reference signal (information signal4502) is gated. In addition, the rectangular wave has pulse amplitudes that are a function of the amplitude of the reference signal (information signal4502). One skilled in the relevant art(s) will recognize the physical limitations to and mathematical obstacles against achieving an exact or perfect rectangular waveform and it is not the intent of the present invention that a perfect rectangular waveform be generated or needed. Again, as stated above, for ease of discussion, the term “rectangular waveform” will be used to refer to waveforms that are substantially rectangular. In a similar manner, the term “square wave” will refer to those waveforms that are substantially square and it is not the intent of the present invention that a perfect square wave be generated or needed.
• As stated before, a harmonically rich signal4506, such as the rectangular wave as indicated inblock1514, has sinusoidal components (harmonics) at frequencies that are integer multiples of the fundamental frequency of the underlying waveform (the Fourier component frequencies). The first three harmonic waveforms are shown inFIGS. 45D, 45E, and45F. In fact, there are an infinite number of harmonics. Instep1516, the unwanted frequencies are removed, and as indicated inblock1518, the remaining frequency is at the desired EM output. As an example, the first (fundamental) harmonic4510 and the second harmonic4512 along with the fourth, fifth, etc., harmonics (not shown) might be filtered out leaving the third harmonic4514 as the desired EM signal as indicated inblock1518.
• The EM signal is prepared for transmission instep1520, and instep1522, the EM signal is transmitted.
• 3.2.3.2 Structural Description.
• FIG. 16 is a block diagram of a transmitter according to an embodiment of the invention. This embodiment of the transmitter is shown as an AM transmitter1600. AM transmitter1600 includes alocal oscillator1610, a summingmodule1606, aswitch module1614, afilter1618, and atransmission module1622 that accepts aninformation signal1602 and outputs a transmittedsignal1624. The operation and structure of exemplary components are described below: an exemplary local oscillator is described below at sections 3.3.2-3.3.2.2; an exemplary a switch module is described below at sections 3.3.7-3.3.7.2; an exemplary filter is described below at sections 3.3.9-3.3.9.2; and an exemplary transmission module is described below at sections 3.3.10-3.3.10.2.
• Preferably, thelocal oscillator1610, summingmodule1606,switch module1614,filter1618, andtransmission module1622 process aninformation signal1602 in the manner shown in theoperational flowchart1500. In other words, AM transmitter1600 is the structural embodiment for performing the operational steps offlowchart1500. However, it should be understood that the scope and spirit of the present invention includes other structural embodiments for performing the steps offlowchart1500. The specifics of these other structural embodiments will be apparent to persons skilled in the relevant art(s) based on the discussion contained herein.
• The operation of the transmitter1600 will now be described in detail with reference to theflowchart1500. Instep1502, information signal1602 (for example, seeFIG. 45A) from a source (not shown) is routed to summing module1606 (if required), thereby producing areference signal1608. Instep1508, anoscillating signal1612 is generated by local oscillator1610 (for example, seeFIG. 45B) and instep1510,switch module1614 gates thereference voltage1608 at a rate that is a function of theoscillating signal1612. The result of the gating is a harmonically rich signal1616 (for example, seeFIG. 45C) with a continuous and periodic waveform. This waveform is preferably a rectangular wave, such as a square wave or a pulse (although, the invention is not limited to this embodiment), and is comprised of a plurality of sinusoidal waves whose frequencies are integer multiples of the fundamental frequency of the waveform. These sinusoidal waves are referred to as the harmonics of the underlying waveform, and a Fourier analysis will determine the relative amplitude of each harmonic (for an example of the first three harmonics, seeFIGS. 45D, 45E, and45F). When amplitude modulation is applied, the amplitude of the pulses inrectangular waveform1616 vary as a function ofreference signal1608. As a result, this change in amplitude of the pulses has a proportional effect on the absolute amplitude of all of the harmonics. In other words, the AM is embedded on top of each of the harmonics. Instep1516, afilter1618 filters out the undesired harmonic frequencies (for example, the first harmonic4510, the second harmonic4512, and the fourth, fifth, etc., harmonics, not shown), and outputs an electromagnetic (EM) signal1620 at the desired harmonic frequency (for example, the third harmonic, seeFIG. 45F). Instep1520,EM signal1620 is routed to transmission module1622 (optional), where it is prepared for transmission. Instep1522, thetransmission module1622 outputs a transmittedsignal1624.
• Note that the description of the AM embodiment given herein shows the information signal being gated, thus applying the amplitude modulation to the harmonically rich signal. However, is would be apparent based on the teachings contained herein, that the information signal can be modulated onto the harmonically rich signal or onto a filtered harmonic at any point in the circuit.
• 3.2.4 Fourth Embodiment: In-phase/Quadrature-phase Modulation (“I/Q”) Mode.
• In-phase/quadrature-phase modulation (“I/Q”) is a specific subset of a phase modulation (PM) embodiment. Because “I/Q” is so pervasive, it is described herein as a separate embodiment. However, it should be remembered that since it is a specific subset of PM, the characteristics of PM also apply to In this embodiment, two information signals are accepted. An in-phase signal (“I”) is modulated such that its phase varies as a function of one of the information signals, and a quadrature-phase signal (“Q”) is modulated such that its phase varies as a function of the other information signal. The two modulated signals are combined to form an “I/Q” modulated signal and transmitted.
• 3.2.4.1 Operational Description.
• The flow chart ofFIG. 17 demonstrates the method of operation of the transmitter in the in-phase/quadrature-phase modulation (“I/Q”) mode. Instep1702, a first information signal is generated by a first source. This information signal may be analog, digital, or any combination thereof. Instep1710, an in-phase oscillating signal (referred to as the “I” signal) is generated and instep1704, it is modulated by the first information signal. This results in the “I” modulated signal as indicated inblock1706 wherein the phase of the “I” modulated signal is varied as a function of the first information signal.
• Instep1714, a second information signal is generated. Again, this signal may be analog, digital, or any combination thereof, and may be different than the first information signal. Instep1712, the phase of “I” oscillating signal generated instep1710 is shifted, creating a quadrature-phase oscillating signal (referred to as the “Q” signal). Instep1716, the “Q” signal is modulated by the second information signal. This results in the “Q” modulated signal as indicated inblock1718 wherein the phase of the “Q” modulated signal is varied as a function of the second information signal.
• An “I” signal with a continuous periodic waveform is generated atstep1708 using the “I” modulated signal, and a “Q” signal with a continuous periodic waveform is generated atstep1720 using the “Q” modulated signal. Instep1722, the “I” periodic waveform and the “Q” periodic waveform are combined forming what is referred to as the “I/Q” periodic waveform as indicated inblock1724. As stated before, a continuous and periodic waveform, such as a “I/Q” rectangular wave as indicated inblock1724, has sinusoidal components (harmonics) at frequencies that are integer multiples of the fundamental frequency of the underlying waveform (the Fourier component frequencies). Instep1726, the unwanted frequencies are removed, and as indicated inblock1728, the remaining frequency is at the desired EM output.
• The “I/Q” EM signal is prepared for transmission instep1730, and instep1732, the “I/Q” EM signal is transmitted.
• 3.2.4.2 Structural Description.
• FIG. 18 is a block diagram of a transmitter according to an embodiment of the invention. This embodiment of the transmitter is shown as an “I/Q” transmitter1800. “I/Q” transmitter1800 includes alocal oscillator1806, aphase shifter1810, twophase modulators1804 &1816, twoswitch modules1822 &1828, asummer1832, afilter1836, and atransmission module1840. The “I/Q” transmitter accepts twoinformation signals1802 &1814 and outputs a transmittedsignal1420. The operation and structure of exemplary components are described below: an exemplary phase modulator is described below at sections 3.3.4-3.3.4.2; an exemplary local oscillator is described below at sections 3.3.2-3.3.2.2; an exemplary phase shifter is described below at sections 3.3.3-3.3.3.2; an exemplary switch module is described below at sections 3.3.6-3.3.6.2; an exemplary summer is described below at sections 3.3.8-3.3.8.2; an exemplary filter is described below at sections 3.3.9-3.3.9.2; and an exemplary transmission module is described below at sections 3.3.10-3.3.10.2.
• Preferably, thelocal oscillator1806,phase shifter1810,phase modulators1804 &1816,switch modules1822 &1828,summer1832,filter1836, andtransmission module1840 process the information signal in the manner shown in theoperational flowchart1700. In other words, “I/Q” transmitter1800 is the structural embodiment for performing the operational steps offlowchart1700. However, it should be understood that the scope and spirit of the present invention includes other structural embodiments for performing the steps offlowchart1700. The specifics of these other structural embodiments will be apparent to persons skilled in the relevant art(s) based on the discussion contained herein.
• The operation of the transmitter1800 will now be described in detail with reference to theflowchart1700 Instep1702, afirst information signal1802 from a source (not shown) is routed to thefirst phase modulator1804. Instep1710, an “I” oscillatingsignal1808 fromlocal oscillator1806 is generated and instep1704, “I” oscillatingsignal1808 is modulated byfirst information signal1802 in thefirst phase modulator1804, thereby producing an “I” modulatedsignal1820. Instep1708, thefirst switch module1822 generates a harmonically rich “I”signal1824 with a continuous and periodic waveform.
• Instep1714, asecond information signal1814 from a source (not shown) is routed to thesecond phase modulator1816. Instep1712, the phase ofoscillating signal1808 is shifted byphase shifter1810 to create “Q” oscillatingsignal1812. Instep1716, “Q” oscillatingsignal1812 is modulated bysecond information signal1814 in thesecond phase modulator1816, thereby producing “Q” modulatedsignal1826. Instep1720, thesecond switch module1828 generates a harmonically rich “Q”signal1830 with a continuous and periodic waveform. Harmonically rich “I”signal1824 and harmonically rich “Q”signal1830 are preferably rectangular waves, such as square waves or pulses (although, the invention is not limited to this embodiment), and are comprised of pluralities of sinusoidal waves whose frequencies are integer multiples of the fundamental frequency of the waveforms. These sinusoidal waves are referred to as the harmonics of the underlying waveforms, and a Fourier analysis will determine the amplitude of each harmonic.
• Instep1722, harmonically rich “I”signal1824 and harmonically rich “Q”signal1830 are combined bysummer1832 to create harmonically rich “I/Q”signal1834. Instep1726, afilter1836 filters out the undesired harmonic frequencies, and outputs an “I/Q” electromagnetic (EM) signal1838 at the desired harmonic frequency. Instep1730, “I/Q”EM signal1838 is routed to transmission module1840 (optional), where it is prepared for transmission. Instep1732, thetransmission module1840 outputs a transmittedsignal1842.
• It will be apparent to those skilled in the relevant art(s) that an alternate embodiment exists wherein the harmonically rich “I”signal1824 and the harmonically rich “Q”signal1830 may be filtered before they are summed, and further, another alternate embodiment exists wherein “I” modulatedsignal1820 and “Q” modulatedsignal1826 may be summed to create an “I/Q” modulated signal before being routed to a switch module.
• 3.2.5 Other Embodiments.
• Other embodiments of the up-converter of the present invention being used as a transmitter (or in other applications) may use subsets and combinations of modulation techniques, and may include modulating one or more information signals as part of the up-conversion process.
• 3.2.5.1 Combination of Modulation Techniques
• Combinations of modulation techniques that would be apparant to those skilled in the relevant art(s) based on the teachings disclosed herein include, but are not limited to, quadrature amplitude modulation (QAM), and embedding two forms of modulation onto a signal for up-conversion.
• An exemplary circuit diagram illustrating the combination of two modulations is found inFIG. 62. This example uses AM combined with PM. The waveforms shown inFIG. 63 illustrate the phase modulation of a digital information signal “A”6202 combined with the amplitude modulation of an analog information signal “B”6204. An oscillating signal6216 (FIG. 63B) and information signal “A”6202 (FIG. 63A) are received byphase modulator1404, thereby creating a phase modulated signal6208 (FIG. 63C). Note that for illustrative purposes, and not limiting, the information signal is shown as a digital signal, and the phase modulation is shown as shifting the phase of the oscillating signal by 180°. Those skilled in the relevant art(s) will appreciate that the information signal could be analog (although typically it is digital), and that phase modulations other than 180° may also be used.FIG. 62 shows apulse shaper6216 receiving phase modulatedsignal6208 and outputting a pulse-shapedPM signal6210. The pulse shaper is optional, depending on the selection and design of thephase modulator1404. Information signal “B”6304 and bias signal1604 (if required) are combined by summing module1606 (optional) to create reference signal6206 (FIG. 63E). Pulse-shapedPM signal6210 is routed to switchmodule1410,1614 where it gates thereference signal6206 thereby producing a harmonically rich signal6212 (FIG. 63F). It can be seen that the amplitude of harmonicallyrich signal6212 varies as a function ofreference signal6206, and the period and pulse width of harmonicallyrich signal6212 are substantially the same as pulse-shapedPM signal6210.FIG. 63 only illustrates the fundamental and second harmonics of harmonicallyrich signal6212. In fact, there may be an infinite number of harmonics, but for illustrative purposes (and not limiting) the first two harmonics are sufficient to illustrate that both the phase modulation and the amplitude modulation that are present on the harmonicallyrich signal6212 are also present on each of the harmonics.Filter1414,1618 will remove the unwanted harmonics, and a desired harmonic6214 is routed totransmission module1418,1622 (optional) where it is prepared for transmission.Transmission module1418,1622 then outputs a transmittedsignal1420,1624. Those skilled in the relevant art(s) will appreciate that these examples are provided for illustrative purposes only and are not limiting.
• The embodiments described above are provided for purposes of illustration. These embodiments are not intended to limit the invention. Alternate embodiments, differing slightly or substantially from those described herein, will be apparent to persons skilled in the relevant art(s) based on the teachings contained herein. Such alternate embodiments include, but are not limited to, combinations of modulation techniques in an “I/Q” mode. Such alternate embodiments fall within the scope and spirit of the present invention.
• 3.3 Methods and Systems for Implementing the Embodiments.
• Exemplary operational and/or structural implementations related to the method(s), structure(s), and/or embodiments described above are presented in this section (and its subsections). These components and methods are presented herein for purposes of illustration, and not limitation. The invention is not limited to the particular examples of components and methods described herein. Alternatives (including equivalents, extensions, variations, deviations, etc., of those described herein) will be apparent to persons skilled in the relevant art(s) based on the teachings contained herein. Such alternatives fall within the scope and spirit of the present invention.
• 3.3.1 The Voltage Controlled Oscillator (FM Mode).
• As discussed above, the frequency modulation (FM) mode embodiment of the invention uses a voltage controlled oscillator (VCO). See, as an example,VCO1204 inFIG. 12. The invention supports numerous embodiments of the VCO. Exemplary embodiments of the VCO2304 (FIG. 23) are described below. However, it should be understood that these examples are provided for illustrative purposes only. The invention is not limited to these embodiments.
• 3.3.1.1 Operational Description.
• Theinformation signal2302 is accepted and anoscillating signal2306 whose frequency varies as a function of theinformation signal2302 is created.Oscillating signal2306 is also referred to as frequency modulatedintermediate signal2306. Theinformation signal2302 may be analog or digital or a combination thereof, and may be conditioned to ensure it is within the desired range.
• In the case where theinformation signal2302 is digital, theoscillating signal2306 may vary between discrete frequencies. For example, in a binary system, a first frequency corresponds to a digital “high,” and a second frequency corresponds to a digital “low.” Either frequency may correspond to the “high” or the “low,” depending on the convention being used. This operation is referred to as frequency shift keying (FSK) which is a subset of FM. If theinformation signal2302 is analog, the frequency of theoscillating signal2306 will vary as a function of that analog signal, and is not limited to the subset of FSK described above.
• Theoscillating signal2306 is a frequency modulated signal which can be a sinusoidal wave, a rectangular wave, a triangular wave, a pulse, or any other continuous and periodic waveform. As stated above, one skilled in the relevant art(s) will recognize the physical limitations to and mathematical obstacles against achieving exact or perfect waveforms and it is not the intent of the present invention that a perfect waveform be generated or needed. Again, as stated above, for ease of discussion, the term “rectangular waveform” will be used to refer to waveforms that are substantially rectangular, the term “square wave” will refer to those waveforms that are substantially square, the term “triangular wave” will refer to those waveforms that are substantially triangular, and the term “pulse” will refer to those waveforms that are substantially a pulse, and it is not the intent of the present invention that a perfect square wave, triangle wave, or pulse be generated or needed.
• 3.3.1.2 Structural Description.
• The design and use of a voltage controlledoscillator2304 is well known to those skilled in the relevant art(s). TheVCO2304 may be designed and fabricated from discrete components, or it may be purchased “off the shelf.”VCO2304 accepts aninformation signal2302 from a source. Theinformation signal2302 is at baseband and generally is an electrical signal within a prescribed voltage range. If the information is digital, the voltage will be at discrete levels. If the information is analog, the voltage will be continuously variable between an upper and a lower level. TheVCO2304 uses the voltage of theinformation signal2302 to cause a modulatedoscillating signal2306 to be output. Theinformation signal2302, because it is a baseband signal and is used to modulate the oscillating signal, may be referred to as the modulatingbaseband signal2302.
• The frequency of theoscillating signal2306 varies as a function of the voltage of the modulatingbaseband signal2302. If the modulatingbaseband signal2302 represents digital information, the frequency of theoscillating signal2306 will be at discrete levels. If, on the other hand, the modulatingbaseband signal2302 represents analog information, the frequency of theoscillating signal2306 will be continuously variable between its higher and lower frequency limits. Theoscillating signal2306 can be a sinusoidal wave, a rectangular wave; a triangular wave, a pulse, or any other continuous and periodic waveform.
• The frequency modulatedoscillating signal2306 may then be used to drive aswitch module2802.
• 3.3.2 The Local Oscillator (PM, AM, and “I/Q” Modes).
• As discussed above, the phase modulation (PM) and amplitude modulation (AM) mode embodiments of the invention use a local oscillator. So too does the in-phase/quadrature-phase modulation (“I/Q”) mode embodiment. See, as an example,local oscillator1406 inFIG. 14,local oscillator1610 inFIG. 16, andlocal oscillator1806 inFIG. 18. The invention supports numerous embodiments of the local oscillator. Exemplary embodiments of the local oscillator2402 (FIG. 24) are described below. However, it should be understood that these examples are provided for illustrative purposes only. The invention is not limited to these embodiments.
• 3.3.2.1 Operational Description.
• Anoscillating signal2404 is generated. The frequency of thesignal2404 may be selectable, but generally is not considered to be “variable.” That is, the frequency may be selected to be a specific value for a specific implementation, but generally it does not vary as a function of the information signal2302 (i.e., the modulating baseband signal).
• Theoscillating signal2404 generally is a sinusoidal wave, but it may also be a rectangular wave, a triangular wave, a pulse, or any other continuous and periodic waveform. As stated above, one skilled in the relevant art(s) will recognize the physical limitations to and mathematical obstacles against achieving exact or perfect waveforms and it is not the intent of the present invention that a perfect waveform be generated or needed. Again, as stated above, for ease of discussion, the term “rectangular waveform” will be used to refer to waveforms that are substantially rectangular, the term “square wave” will refer to those waveforms that are substantially square, the term “triangular wave” will refer to those waveforms that are substantially triangular, and the term “pulse” will refer to those waveforms that are substantially a pulse, and it is not the intent of the present invention that a perfect square wave, triangle wave, or pulse be generated or needed.
• 3.3.2.2 Structural Description.
• The design and use of alocal oscillator2402 is well known to those skilled in the relevant art(s). Alocal oscillator2402 may be designed and fabricated from discrete components or it may be purchased “off the shelf.” Alocal oscillator2402 is generally set to output a specific frequency. The output can be “fixed” or it can be “selectable,” based on the design of the circuit. If it is fixed, the output is considered to be substantially a fixed frequency that cannot be changed. If the output frequency is selectable, the design of the circuit will allow a control signal to be applied to thelocal oscillator2402 to change the frequency for different applications. However, the output frequency of alocal oscillator2402 is not considered to be “variable” as a function of aninformation signal2302 such as the modulatingbaseband signal2302. (If it were desired for the output frequency of an oscillator to be variable as a function of an information signal, a VCO would preferably be used.) Theoscillating signal2404 generally is a sinusoidal wave, but it may also be a rectangular wave, a triangular wave, a pulse, or any other continuous and periodic waveform.
• The output of alocal oscillator2402 may be an input to other circuit components such as aphase modulator2606, aphase shifting circuit2504,switch module3102, etc.
• 3.3.3 The Phase Shifter (“I/Q” Mode).
• As discussed above, the in-phase/quadrature-phase modulation (“I/Q”) mode embodiment of the invention uses a phase shifter. See, as an example,phase shifter1810 inFIG. 18. The invention supports numerous embodiments of the phase shifter. Exemplary embodiments of the phase shifter2504 (FIG. 25) are described below. The invention is not limited to these embodiments. The description contained herein is for a “90° phase shifter.” The 90° phase shifter is used for ease of explanation, and one skilled in the relevant art(s) will understand that other phase shifts can be used without departing from the intent of the present invention.
• 3.3.3.1 Operational Description.
• An “in-phase” oscillatingsignal2502 is received and a “quadrature-phase” oscillatingsignal2506 is output. If the in-phase (“I”)signal2502 is referred to as being a sine wave, then the quadrature-phase (“Q”)signal2506 can be referred to as being a cosine wave (i.e., the “Q”signal2506 is 90° out of phase with the “I” signal2502). However, they may also be rectangular waves, triangular waves, pulses, or any other continuous and periodic waveforms. As stated above, one skilled in the relevant art(s) will recognize the physical limitations to and mathematical obstacles against achieving exact or perfect waveforms and it is not the intent of the present invention that a perfect waveform be generated or needed. Again, as stated above, for ease of discussion, the term “rectangular waveform” will be used to refer to waveforms that are substantially rectangular, the term “square wave” will refer to those waveforms that are substantially square, the term “triangular wave” will refer to those waveforms that are substantially triangular, and the term “pulse” will refer to those waveforms that are substantially a pulse, and it is not the intent of the present invention that a perfect square wave, triangle wave, or pulse be generated or needed. Regardless of the shapes of the waveforms, the “Q”signal2506 is out of phase with the “I”signal2506 by one-quarter period of the waveform. The frequency of the “I” and “Q” signals2502 and2506 are substantially equal.
• The discussion contained herein will be confined to the more-prevalent embodiment wherein there are two intermediate signals separated by 90°. This is not limiting on the invention. It will be apparent to those skilled in the relevant art(s) that the techniques tough herein and applied to the “I/Q” embodiment of the present invention also apply to more exotic embodiments wherein the intermediate signals are shifted by some amount other than 90°, and also wherein there may be more than two intermediate frequencies.
• 3.3.3.2 Structural Description.
• The design and use of aphase shifter2504 is well known to those skilled in the relevant art(s). Aphase shifter2504 may be designed and fabricated from discrete components or it may be purchased “off the shelf.” A phase shifter accepts an “in-phase” (“I”) oscillatingsignal2502 from any of a number of sources, such as aVCO2304 or alocal oscillator2402, and outputs a “quadrature-phase” (“Q”) oscillatingsignal2506 that is substantially the same frequency and substantially the same shape as the incoming “I”signal2502, but with the phase shifted by 90°. Both the “I” and “Q” signals2502 and2506 are generally sinusoidal waves, but they may also be rectangular waves, triangular waves, pulses, or any other continuous and periodic waveforms. Regardless of the shapes of the waveforms, the “Q”signal2506 is out of phase with the “I”signal2502 by one-quarter period of the waveform. Both the “I” and “Q” signals2502 and2506 may be modulated.
• The output of aphase shifter2504 may be used as an input to aphase modulator2606.
• 3.3.4 The Phase Modulator (PM and “I/Q” Modes).
• As discussed above, the phase modulation (PM) mode embodiment including the in-phase/quadrature-phase modulation (“I/Q”) mode embodiment of the invention uses a phase modulator. See, as an example,phase modulator1404 ofFIG. 14 andphase modulators1804 and1816 ofFIG. 18. The invention supports numerous embodiments of the phase modulator. Exemplary embodiments of the phase modulator2606 (FIG. 26) are described below. However, it should be understood that these examples are provided for illustrative purposes only. The invention is not limited to these embodiments.
• 3.3.4.1 Operational Description.
• Aninformation signal2602 and anoscillating signal2604 are accepted, and a phase modulatedoscillating signal2608 whose phase varies as a function of theinformation signal2602 is output. Theinformation signal2602 may be analog or digital and may be conditioned to ensure it is within the desired range. Theoscillating signal2604 can be a sinusoidal wave, a rectangular wave, a triangular wave, a pulse, or any other continuous and periodic waveform. As stated above, one skilled in the relevant art(s) will recognize the physical limitations to and mathematical obstacles against achieving exact or perfect waveforms and it is not the intent of the present invention that a perfect waveform be generated or needed. Again, as stated above, for ease of discussion, the term “rectangular waveform” will be used to refer to waveforms that are substantially rectangular, the term “square wave” will refer to those waveforms that are substantially square, the term “triangular wave” will refer to those waveforms that are substantially triangular, and the term “pulse” will refer to those waveforms that are substantially a pulse, and it is not the intent of the present invention that a perfect square wave, triangle wave, or pulse be generated or needed. The modulatedoscillating signal2608 is also referred to as the modulatedintermediate signal2608.
• In the case where theinformation signal2602 is digital, the modulatedintermediate signal2608 will shift phase between discrete values, the first phase (e.g., for a signal represented by sin (ωt+θ_o)) corresponding to a digital “high,” and the second phase (e.g., for a signal represented by sin (ωt+θ_o+δ), where δ represents the amount the phase has been shifted) corresponding to a digital “low.” Either phase may correspond to the “high” or the “low,” depending on the convention being used. This operation is referred to as phase shift keying (PSK) which is a subset of PM.
• If theinformation signal2602 is analog, the phase of the modulatedintermediate signal2608 will vary as a function of theinformation signal2602 and is not limited to the subset of PSK described above.
• The modulatedintermediate signal2608 is a phase modulated signal which can be a sinusoidal wave, a rectangular wave, a triangular wave, a pulse, or any other continuous and periodic waveform, and which has substantially the same period as theoscillating signal2604.
• 3.3.4.2 Structural Description.
• The design and use of aphase modulator2606 is well known to those skilled in the relevant art(s). Aphase modulator2606 may be designed and fabricated from discrete components, or it may be purchased “off the shelf.” Aphase modulator2606 accepts aninformation signal2602 from a source and anoscillating signal2604 from alocal oscillator2402 or aphase shifter2504. Theinformation signal2602 is at baseband and is generally an electrical signal within a prescribed voltage range. If the information is digital, the voltage will be at discrete levels. If the information is analog, the voltage will be continuously variable between an upper and a lower level as a function of theinformation signal2602. Thephase modulator2606 uses the voltage of theinformation signal2602 to modulate theoscillating signal2604 and causes a modulatedintermediate signal2608 to be output. Theinformation signal2602, because it is a baseband signal and is used to modulate the oscillating signal, may be referred to as the modulatingbaseband signal2604.
• The modulatedintermediate signal2608 is an oscillating signal whose phase varies as a function of the voltage of the modulatingbaseband signal2602. If the modulatingbaseband signal2602 represents digital information, the phase of the modulatedintermediate signal2608 will shift by a discrete amount (e.g., the modulatedintermediate signal2608 will shift by an amount δ between sin (ωt+θ_o) and sin (ωt+θ_o+δ). If, on the other hand, the modulatingbaseband signal2602 represents analog information, the phase of the modulatedintermediate signal2608 will continuously shift between its higher and lower phase limits as a function of theinformation signal2602. In one exemplary embodiment, the upper and lower limits of the modulatedintermediate signal2608 can be represented as sin(ωt+θ_o) and sin(ωt+θ_o+π). In other embodiments, the range of the phase shift may be less than π. The modulatedintermediate signal2608 can be a sinusoidal wave, a rectangular wave, a triangular wave, a pulse, or any other continuous and periodic waveform.
• The phase modulatedintermediate signal2608 may then be used to drive aswitch module2802.
• 3.3.5 The Summing Module (AM Mode).
• As discussed above, the amplitude modulation (AM) mode embodiment of the invention uses a summing module. See, as an example, summingmodule1606 inFIG. 16. The invention supports numerous embodiments of the summing module. Exemplary embodiments of the summing module2706 (FIG. 27) are described below. However, it should be understood that these examples are provided for illustrative purposes only. The invention is not limited to these embodiments. It may also be used in the “I/Q” mode embodiment when the modulation is AM. The summingmodule2706 need not be used in all AM embodiments.
• 3.3.5.1 Operational Description.
• Aninformation signal2702 and abias signal2702 are accepted, and a reference signal is output. Theinformation signal2702 may be analog or digital and may be conditioned to ensure it is within the proper range so as not to damage any of the circuit components. Thebias signal2704 is usually a direct current (DC) signal.
• In the case where theinformation signal2702 is digital, thereference signal2706 shifts between discrete values, the first value corresponding to a digital “high,” and the second value corresponding to a digital “low.” Either value may correspond to the “high” or the “low,” depending on the convention being used. This operation is referred to as amplitude shift keying (ASK) which is a subset of AM.
• If theinformation signal2702 is analog, the value of thereference signal2708 will vary linearly between upper and lower extremes which correspond to the upper and lower limits of theinformation signal2702. Again, either extreme of thereference signal2708 range may correspond to the upper or lower limit of theinformation signal2702 depending on the convention being used.
• Thereference signal2708 is a digital or analog signal and is substantially proportional to theinformation signal2702.
• 3.3.5.2 Structural Description.
• The design and use of a summingmodule2706 is well known to those skilled in the relevant art(s). A summingmodule2706 may be designed and fabricated from discrete components, or it may be purchased “off the shelf.” A summingmodule2706 accepts aninformation signal2702 from a source. Theinformation signal2702 is at baseband and generally is an electrical signal within a prescribed voltage range. If the information is digital, theinformation signal2702 is at either of two discrete levels. If the information is analog, theinformation signal2702 is continuously variable between an upper and a lower level. The summingmodule2706 uses the voltage of theinformation signal2702 and combines it with abias signal2704. The output of the summingmodule2706 is called thereference signal2708. The purpose of the summingmodule2706 is to cause thereference signal2708 to be within a desired signal range. One skilled in the relevant art(s) will recognize that theinformation signal2702 may be used directly, without being summed with abias signal2704, if it is already within the desired range. Theinformation signal2702 is a baseband signal, but typically, in an AM embodiment, it is not used to directly modulate an oscillating signal. The amplitude of thereference signal2708 is at discrete levels if theinformation signal2702 represents digital information. On the other hand, the amplitude of thereference signal2708 is continuously variable between its, higher and lower limits if theinformation signal2702 represents analog information. The amplitude of thereference signal2708 is substantially proportional to theinformation signal2702, however, apositive reference signal2708 need not represent apositive information signal2702.
• Thereference signal2708 is routed to thefirst input3108 of aswitch module3102. In one exemplary embodiment, aresistor2824 is connected between the output of the summing module2706 (or the source of theinformation signal2702 in the embodiment wherein the summingamplifier2706 is not used) and theswitch3116 of theswitch module3102.
• 3.3.6 The Switch Module (FM PM, and “I/Q” Modes).
• As discussed above, the frequency modulation (FM), phase modulation (PM), and the in-phase/quadrature-phase modulation (“I/Q”) mode embodiments of the invention use a switching assembly referred to as switch module2802 (FIGS. 28A-28C). As an example,switch module2802 is a component inswitch module1214 inFIG. 12,switch module1410 inFIG. 14, andswitch modules1822 and1828 inFIG. 18. The invention supports numerous embodiments of the switch module. Exemplary embodiments of theswitch module2802 are described below. However, it should be understood that these examples are provided for illustrative purposes only. The invention is not limited to these embodiments. Theswitch module2802 and its operation in the FM, PM, and “I/Q” mode embodiments is substantially the same as its operation in the AM mode embodiment, described in sections 3.3.7-3.3.7.2 below.
• 3.3.6.1 Operational Description.
• Abias signal2806 is gated as a result of the application of a modulatedoscillating signal2804, and a signal with a harmonicallyrich waveform2814 is created. Thebias signal2806 is generally a fixed voltage. The modulatedoscillating signal2804 can be frequency modulated, phase modulated, or any other modulation scheme or combination thereof. In certain embodiments, such as in certain amplitude shift keying modes, the modulatedoscillating signal2804 may also be amplitude modulated. The modulatedoscillating signal2804 can be a sinusoidal wave, a rectangular wave, a triangular wave, a pulse, or any other continuous and periodic waveform. In a preferred embodiment, modulatedoscillating signal2804 would be a rectangular wave. As stated above, one skilled in the relevant art(s) will recognize the physical limitations to and mathematical obstacles against achieving exact or perfect waveforms and it is not the intent of the present invention that a perfect waveform be generated or needed. Again, as stated above, for ease of discussion, the term “rectangular waveform” will be used to refer to waveforms that are substantially rectangular, the term “square wave” will refer to those waveforms that are substantially square, the term “triangular wave” will refer to those waveforms that are substantially triangular, and the term “pulse” will refer to those waveforms that are substantially a pulse, and it is not the intent of the present invention that a perfect square wave, triangle wave, or pulse be generated or needed.
• The signal with harmonicallyrich waveform2814, hereafter referred to as the harmonicallyrich signal2814, is a continuous and periodic waveform that is modulated substantially the same as the modulatedoscillating signal2804. That is, if the modulatedoscillating signal2804 is frequency modulated, the harmonicallyrich signal2814 will also be frequency modulated, and if the modulatedoscillating signal2804 is phase modulated, the harmonicallyrich signal2814 will also be phase modulated. (In one embodiment, the harmonicallyrich signal2814 is a substantially rectangular waveform.) As stated before, a continuous and periodic waveform, such as a rectangular wave, has sinusoidal components (harmonics) at frequencies that are integer multiples of the fundamental frequency of the underlying waveform (the Fourier component frequencies). Thus, the harmonicallyrich signal2814 is composed of sinusoidal signals at frequencies that are integer multiples of the fundamental frequency of itself.
• 3.3.6.2 Structural Description.
• Theswitch module2802 of an embodiment of the present invention is comprised of afirst input2808, asecond input2810, acontrol input2820, anoutput2822, and aswitch2816. Abias signal2806 is applied to thefirst input2808 of theswitch module2802. Generally, thebias signal2806 is a fixed voltage, and in one embodiment of the invention, aresistor2824 is located between thebias signal2806 and theswitch2816. Thesecond input2810 of theswitch module2802 is generally atelectrical ground2812. However, one skilled in the relevant art(s) will recognize that alternative embodiments exist wherein thesecond input2810 may not be atelectrical ground2812, but rather asecond signal2818, provided that thesecond signal2818 is different than thebias signal2806.
• A modulatedoscillating signal2804 is connected to thecontrol input2820 of theswitch module2802. The modulatedoscillating signal2804 may be frequency modulated or phase modulated. (In some circumstances and embodiments, it may be amplitude modulated, such as in on/off keying, but this is not the general case, and will not be described herein.) The modulatedoscillating signal2804 can be a sinusoidal wave, a rectangular wave, a triangular wave, a pulse, or any other continuous and periodic waveform. In a preferred embodiment, it would be a rectangular wave. The modulatedoscillating signal2804 causes theswitch2816 to close and open.
• The harmonicallyrich signal2814 described in section 3.3.6.1 above, is found at theoutput2822 of theswitch module2802. The harmonicallyrich signal2814 is a continuous and periodic waveform that is modulated substantially the same as the modulatedoscillating signal2804. That is, if the modulatedoscillating signal2804 is frequency modulated, the harmonicallyrich signal2814 will also be frequency modulated, and if the modulatedoscillating signal2804 is phase modulated, the harmonicallyrich signal2814 will also be phase modulated. In one embodiment, the harmonicallyrich signal2814 has a substantially rectangular waveform. As stated before, a continuous and periodic waveform, such as a rectangular wave, has sinusoidal components (harmonics) at frequencies that are integer multiples of the fundamental frequency of the underlying waveform (the Fourier component frequencies). Thus, the harmonicallyrich signal2814 is composed of sinusoidal signals at frequencies that are integer multiples of the fundamental frequency of itself. Each of these sinusoidal signals is also modulated substantially the same as the continuous and periodic waveform (i.e., the modulated oscillating signal2804) from which it is derived.
• Theswitch module2802 operates as follows. When theswitch2816 is “open,” theoutput2822 ofswitch module2802 is at substantially the same voltage level asbias signal2806. Thus, since the harmonicallyrich signal2814 is connected directly to theoutput2822 ofswitch module2802, the amplitude of harmonicallyrich signal2814 is equal to the amplitude of thebias signal2806. When the modulatedoscillating signal2804 causes theswitch2816 to become “closed,” theoutput2822 ofswitch module2802 becomes connected electrically to thesecond input2810 of switch module2802 (e.g.,ground2812 in one embodiment of the invention), and the amplitude of the harmonicallyrich signal2814 becomes equal to the potential present at the second input2810 (e.g., zero volts for the embodiment wherein thesecond input2810 is connected to electrical ground2812). When the modulatedoscillating signal2804 causes theswitch2816 to again become “open,” the amplitude of the harmonicallyrich signal2814 again becomes equal to thebias signal2806. Thus, the amplitude of the harmonicallyrich signal2814 is at either of two signal levels, i.e.,bias signal2806 orground2812, and has a frequency that is substantially equal to the frequency of the modulatedoscillating signal2804 that causes theswitch2816 to open and close. The harmonicallyrich signal2814 is modulated substantially the same as the modulatedoscillating signal2804. One skilled in the relevant art(s) will recognize that any one of a number of switch designs will fulfill the scope and spirit of the present invention as described herein.
• In an embodiment of the invention, theswitch2816 is a semiconductor device, such as a diode ring. In another embodiment, the switch is a transistor, such as a field effect transistor (FET). In an embodiment wherein the FET is gallium arsenide (GaAs),switch module2802 can be designed as seen inFIGS. 29A-29C, where the modulatedoscillating signal2804 is connected to thegate2902 of theGaAsFET2901, thebias signal2806 is connected through abias resistor2824 to thesource2904 of theGaAsFET2901, andelectrical ground2812 is connected to thedrain2906 ofGaAsFET2901. (In an alternate embodiment shown inFIG. 29C, asecond signal2818 may be connected to thedrain2906 ofGaAsFET2901.) Since the drain and the source of GaAsFETs are interchangeable, thebias signal2806 can be applied to either thesource2904 or to thedrain2906. If there is concern that there might be some source-drain asymmetry in the GaAsFET, the switch module can be designed as shown inFIGS. 30A-30C, wherein twoGaAsFETs3002 and3004 are connected together, with thesource3010 of the first3002 connected to thedrain3012 of the second3004, and thedrain3006 of the first3002 being connected to thesource3008 of the second3004. This design arrangement will balance substantially all asymmetries.
• An alternate implementation of the design includes a “dwell capacitor” wherein one side of a capacitor is connected to the first input of the switch and the other side of the capacitor is connected to the second input of the switch. The purpose of the design is to increase the apparent aperture of the pulse without actually increasing its width. For additional detail on the design and use of a dwell capacitor, see co-pending application entitled “Method and System for Down-Converting Electromagnetic Signals Having Optimized Switch Structures,” Attorney Docket No. 1744.0010001, and other applications as referenced above.
• Other switch designs and implementations will be apparent to persons skilled in the relevant art(s).
• Theoutput2822 of theswitch module2802, i.e., the harmonicallyrich signal2814, can be routed to afilter3504 in the FM and PM modes or to aSummer3402 in the “I/Q” mode.
• 3.3.7 The Switch Module (AM Mode).
• As discussed above, the amplitude modulation (AM) mode embodiment of the invention uses a switching assembly referred to as switch module3102 (FIGS. 31A-31C). As an example,switch module3102 is a component inswitch module1614 ofFIG. 16. The invention supports numerous embodiments of the switch module. Exemplary embodiments of theswitch module3102 are described below. However, it should be understood that these examples are provided for illustrative purposes only. The invention is not limited to these embodiments. Theswitch module3102 and its operation in the AM mode embodiment is substantially the same as its operation in the FM, PM, and “I/Q” mode embodiments described in sections 3.3.6-3.3.6.2 above.
• 3.3.7.1 Operational Description.
• Areference signal3106 is gated as a result of the application of anoscillating signal3104, and a signal with a harmonicallyrich waveform3114 is created. Thereference signal3106 is a function of theinformation signal2702 and may, for example, be either the summation of theinformation signal2702 with abias signal2704 or it may be theinformation signal2702 by itself. In the AM mode, theoscillating signal3104 is generally not modulated, but can be.
• Theoscillating signal3104 can be a sinusoidal wave, a rectangular wave, a triangular wave, a pulse, or any other continuous and periodic waveform. In a preferred embodiment, it would be a rectangular wave. As stated above, one skilled in the relevant art(s) will recognize the physical limitations to and mathematical obstacles against achieving exact or perfect waveforms and it is not the intent of the present invention that a perfect waveform be generated or needed. Again, as stated above, for ease of discussion, the term “rectangular waveform” will be used to refer to waveforms that are substantially rectangular, the term “square wave” will refer to those waveforms that are substantially square, the term “triangular wave” will refer to those waveforms that are substantially triangular, and the term “pulse” will refer to those waveforms that are substantially a pulse, and it is not the intent of the present invention that a perfect square wave, triangle wave, or pulse be generated or needed.
• The signal with a harmonicallyrich waveform3114, hereafter referred to as the harmonicallyrich signal3114, is a continuous and periodic waveform whose amplitude is a function of the reference signal. That is, it is an AM signal. In one embodiment, the harmonicallyrich signal3114 has a substantially rectangular waveform. As stated before, a continuous and periodic waveform, such as a rectangular wave, will have sinusoidal components (harmonics) at frequencies that are integer multiples of the fundamental frequency of the underlying waveform (the Fourier component frequencies). Thus, harmonicallyrich signal3114 is composed of sinusoidal signals at frequencies that are integer multiples of the fundamental frequency of itself.
• Those skilled in the relevant art(s) will recognize that alternative embodiments exist wherein combinations of modulations (e.g., PM and ASK, FM and AM, etc.) may be employed simultaneously. In these alternate embodiments, theoscillating signal3104 may be modulated. These alternate embodiments will be apparent to persons skilled in the relevant art(s), and thus will not be described herein.
• 3.3.7.2 Structural Description.
• Theswitch module3102 of the present invention is comprised of afirst input3108, asecond input3110, acontrol input3120, anoutput3122, and aswitch3116. Areference signal3106 is applied to thefirst input3108 of theswitch module3102. Generally, thereference signal3106 is a function of theinformation signal2702, and may either be the summation of theinformation signal2702 with a bias signal or it may be theinformation signal2702 by itself. In one embodiment of the invention, aresistor3124 is located between thereference signal3106 and theswitch3116. Thesecond input3110 of theswitch module3102 is generally atelectrical ground3112, however, one skilled in the relevant art(s) will recognize that alternative embodiments exist wherein thesecond input3110 may not be atelectrical ground3112, but rather connected to asecond signal3118. In an alternate embodiment, the inverted value of thereference signal3106 is connected to thesecond input3110 of theswitch module3102.
• Anoscillating signal3104 is connected to thecontrol input3120 of theswitch module3102. Generally, in the AM mode, theoscillating signal3104 is not modulated, but a person skilled in the relevant art(s) will recognize that there are embodiments wherein theoscillating signal3104 may be frequency modulated or phase modulated, but these will not be described herein. Theoscillating signal3104 can be a sinusoidal wave, a rectangular wave, a triangular wave, a pulse, or any other continuous and periodic waveform. In a preferred embodiment, it would be a rectangular wave. Theoscillating signal3104 causes theswitch3116 to close and open.
• The harmonicallyrich signal3114 described in section 3.3.7.1 above is found at theoutput3122 of theswitch module3102. The harmonicallyrich signal3114 is a continuous and periodic waveform whose amplitude is a function of the amplitude of the reference signal. In one embodiment, the harmonicallyrich signal3114 has a substantially rectangular waveform. As stated before, a continuous and periodic waveform, such as a rectangular wave, has sinusoidal components (harmonics) at frequencies that are integer multiples of the fundamental frequency of the underlying waveform (the Fourier component frequencies). Thus, harmonicallyrich signal3114 is composed of sinusoidal signals at frequencies that are integer multiples of the fundamental frequency of itself. As previously described, the relative amplitude of the harmonics of a continuous periodic waveform is generally a function of the ratio of the pulse width of the rectangular wave and the period of the fundamental frequency, and can be determined by doing a Fourier analysis of the periodic waveform. When the amplitude of the periodic waveform varies, as in the AM mode of the invention, the change in amplitude of the periodic waveform has a proportional effect on the absolute amplitude of the harmonics. In other words, the AM is embedded on top of each of the harmonics.
• The description of theswitch module3102 is substantially as follows: When theswitch3116 is “open,” the amplitude of the harmonicallyrich signal3114 is substantially equal to thereference signal3106. When theoscillating signal3104 causes theswitch3116 to become “closed,” theoutput3122 of theswitch module3102 becomes connected electrically to thesecond input3110 of the switch module3102 (e.g.,ground3112 in one embodiment), and the amplitude of the harmonicallyrich signal3114 becomes equal to the value of the second input3110 (e.g., zero volts for the embodiment wherein thesecond input3110 is connected to electrical ground3112). When theoscillating signal3104 causes theswitch3116 to again become “open,” the amplitude of the harmonicallyrich signal3114 again becomes substantially equal to thereference signal3106. Thus, the amplitude of the harmonicallyrich signal3114 is at either of two signal levels, i.e.,reference signal3106 orground3112, and has a frequency that is substantially equal to the frequency of theoscillating signal3104 that causes theswitch3116 to open and close. In an alternate embodiment wherein thesecond input3110 is connected to thesecond signal3118, the harmonicallyrich signal3114 varies between thereference signal3106 and thesecond signal3118. One skilled in the relevant art(s) will recognize that any one of a number of switch module designs will fulfill the scope and spirit of the present invention.
• In an embodiment of the invention, theswitch3116 is a semiconductor device, such as a diode ring. In another embodiment, the switch is a transistor, such as, but not limited to, a field effect transistor (FET). In an embodiment wherein the FET is gallium arsenide (GaAs), the module can be designed as seen inFIGS. 32A-32C, where theoscillating signal3104 is connected to thegate3202 of theGaAsFET3201, thereference signal3106 is connected to thesource3204, andelectrical ground3112 is connected to the drain3206 (in the embodiment whereground3112 is selected as the value of thesecond input3110 of the switch module3102). Since the drain and the source of GaAsFETs are interchangeable, thereference signal3106 can be applied to either thesource3204 or to thedrain3206. If there is concern that there might be some source-drain asymmetry in theGaAsFET3201, theswitch3116 can be designed as shown inFIGS. 33A-33C, wherein twoGaAsFETs3302 and3304 are connected together, with thesource3310 of the first3302 connected to thedrain3312 of the second3304, and thedrain3306 of the first3302 being connected to thesource3308 of the second3304. This design arrangement will substantially balance all asymmetries.
• An alternate implementation of the design includes a “dwell capacitor” wherein one side of a capacitor is connected to the first input of the switch and the other side of the capacitor is connected to the second input of the switch. The purpose of the design is to increase the apparent aperture of the pulse without actually increasing its width. For additional detail on the design and use of a dwell capacitor, see co-pending application entitled “Method and System for Down-Converting Electromagnetic Signals Having Optimized Switch Structures,” Attorney Docket No. 1744.0010001, and other applications as referenced above.
• Other switch designs and implementations will be apparent to persons skilled in the relevant art(s).
• Theoutput3122 of theswitch module3102, i.e., the harmonicallyrich signal3114, can be routed to afilter3504 in the AM mode.
• 3.3.8 The Summer (“I/Q” Mode).
• As discussed above, the in-phase/quadrature-phase modulation (“I/Q”) mode embodiment of the invention uses a summer. See, as an example,summer1832 inFIG. 18. The invention supports numerous embodiments of the summer. Exemplary embodiments of the summer3402 (FIG. 34) are described below. However, it should be understood that these examples are provided for illustrative purposes only. The invention is not limited to these embodiments.
• 3.3.8.1 Operational Description.
• An “I” modulatedsignal3404 and a “Q” modulatedsignal3406 are combined and an “I/Q” modulatedsignal3408 is generated. Generally, both “I” and “Q” modulatedsignals3404 and3406 are harmonically rich waveforms, which are referred to as the harmonically rich “I”signal3404 and the harmonically rich “Q”signal3406. Similarly, “I/Q” modulatedsignal3408 is harmonically rich and is referred to as the harmonically rich “I/Q” signal. In one embodiment, these harmonically rich signals have substantially rectangular waveforms. As stated above, one skilled in the relevant art(s) will recognize the physical limitations to and mathematical obstacles against achieving exact or perfect waveforms and it is not the intent of the present invention that a perfect waveform be generated or needed.
• In a typical embodiment, the harmonically rich “I”signal3404 and the harmonically rich “Q”signal3406 are phase modulated, as is the harmonically rich “I/Q”signal3408. A person skilled in the relevant art(s) will recognize that other modulation techniques, such as amplitude modulating the “I/Q” signal, may also be used in the “I/Q” mode without deviating from the scope and spirit of the invention.
• As stated before, a continuous and periodic waveform, such as harmonically rich “I/Q”signal3408, has sinusoidal components (harmonics) at frequencies that are integer multiples of the fundamental frequency of the underlying waveform (the Fourier component frequencies). Thus, harmonically rich “I/Q”signal3408 is composed of sinusoidal signals at frequencies that are integer multiples of the fundamental frequency of itself. These sinusoidal signals are also modulated substantially the same as the continuous and periodic waveform from which they are derived. That is, in this embodiment, the sinusoidal signals are phase modulated, and include the information from both the “I” modulated signal and the “Q” modulated signal.
• 3.3.8.2 Structural Description.
• The design and use of asummer3402 is well known to those skilled in the relevant art(s). Asummer3402 may be designed and fabricated from discrete components, or it may be purchased “off the shelf.” Asummer3402 accepts a harmonically rich “I”signal3404 and a harmonically rich “Q”signal3406, and combines them to create a harmonically rich “I/Q”signal3408. In a preferred embodiment of the invention, the harmonically rich “I”signal3404 and the harmonically rich “Q”signal3406 are both phase modulated. When the harmonically rich “I”signal3404 and the harmonically rich “Q”signal3406 are both phase modulated, the harmonically rich “I/Q”signal3408 is also phase modulated.
• As stated before, a continuous and periodic waveform, such as the harmonically rich “I/Q”signal3408, has sinusoidal components (harmonics) at frequencies that are integer multiples of the fundamental frequency of the underlying waveform (the Fourier component frequencies). Thus, the harmonically rich “I/Q”signal3408 is composed of “I/Q” sinusoidal signals at frequencies that are integer multiples of the fundamental frequency of itself. These “I/Q” sinusoidal signals are also phase modulated substantially the same as the continuous and periodic waveform from which they are derived (i.e., the harmonically rich “I/Q” signal3408).
• The output of thesummer3402 is then routed to afilter3504.
• 3.3.9 The Filter (FM, PM, AM, and “I/Q” Modes).
• As discussed above, all modulation mode embodiments of the invention use a filter. See, as an example,filter1218 inFIG. 12,filter1414 inFIG. 14,filter1618 inFIG. 16, andfilter1836 inFIG. 18. The invention supports numerous embodiments of the filter. Exemplary embodiments of the filter3504 (FIG. 35) are described below. However, it should be understood that these examples are provided for illustrative purposes only. The invention is not limited to these embodiments.
• 3.3.9.1 Operational Description.
• A modulated signal with a harmonicallyrich waveform3502 is accepted. It is referred to as the harmonicallyrich signal3502. As stated above, a continuous and periodic waveform, such as the harmonicallyrich signal3502, is comprised of sinusoidal components (harmonics) at frequencies that are integer multiples of the fundamental frequency of the underlying waveform from which they are derived. These are called the Fourier component frequencies. In one embodiment of the invention, the undesired harmonic frequencies are removed, and the desiredfrequency3506 is output. In an alternate embodiment, a plurality of harmonic frequencies are output.
• The harmonic components of the harmonicallyrich signal3502 are modulated in the same manner as the harmonicallyrich signal3502 itself. That is, if the harmonicallyrich signal3502 is frequency modulated, all of the harmonic components of that signal are also frequency modulated. The same is true for phase modulation, amplitude modulation, and “I/Q” modulation.
• 3.3.9.2 Structural Description.
• The design and use of afilter3504 is well known to those skilled in the relevant art(s). Afilter3504 may be designed and fabricated from discrete components or it may be purchased “off the shelf.” Thefilter3504 accepts the harmonicallyrich signal3502 from theswitch module2802 or3102 in the FM, PM, and AM modes, and from thesummer3402 in the “I/Q” mode. The harmonicallyrich signal3502 is a continuous and periodic waveform. As such, it is comprised of sinusoidal components (harmonics) that are at frequencies that are integer multiples of the fundamental frequency of the underlying harmonicallyrich signal3502. Thefilter3504 removes those sinusoidal signals having undesired frequencies. Thesignal3506 that remains is at the desired frequency, and is called the desiredoutput signal3506.
• To achieve this result, according to an embodiment of the invention, afilter3504 is required to filter out the unwanted harmonics of the harmonicallyrich signal3502.
• The term “Q” is used to represent the ratio of the center frequency of the desiredoutput signal3506 to the half power band width. Looking atFIG. 36 we see a desiredfrequency3602 of 900 MHz. Thefilter3504 is used to ensure that only the energy at thatfrequency3602 is transmitted. Thus, thebandwidth3604 at half power (the so-called “3 dB down” point) should be as narrow as possible. The ratio offrequency3602 tobandwidth3604 is defined as “Q.” As shown onFIG. 36, if the “3 dB down” point is at plus or minus 15 MHz, the value of Q will be 900÷(15+15) or 30. With the proper selection of elements for any particular frequency, Qs on the order of 20 or 30 are achievable.
• For crisp broadcast frequencies, it is desired that Q be as high as possible and practical, based on the given application and environment. The purpose of thefilter3504 is to filter out the unwanted harmonics of the harmonically rich signal. The circuits are tuned to eliminate all other harmonics except for the desired frequency3506 (e.g., the 900 MHz harmonic3602). Turning now toFIGS. 37A and 37B, we see examples of filter circuits. One skilled in the relevant art(s) will recognize that a number of filter designs will accomplish the desired goal of passing the desired frequency while filtering the undesired frequencies.
• FIG. 37A illustrates a circuit having a capacitor in parallel with an inductor and shunted to ground. InFIG. 37B, a capacitor is in series with an inductor, and a parallel circuit similar to that inFIG. 37A is connected between the capacitor and inductor and shunted to ground.
• The modulated signal at the desiredfrequency3506 may then be routed to thetransmission module3804.
• 3.3.10 The Transmission Module (FM, PM, AM, and “I/Q” Modes).
• As discussed above, the modulation mode embodiments of the invention preferably use a transmission module. See, as an example,transmission module1222 inFIG. 12,transmission module1418 inFIG. 14,transmission module1622 inFIG. 16, andtransmission module1840 inFIG. 18. The transmission module is optional, and other embodiments may not include a transmission module. The invention supports numerous embodiments of the transmission module. Exemplary embodiments of the transmission module3804 (FIG. 38) are described below. However, it should be understood that these examples are provided for illustrative purposes only. The invention is not limited to these embodiments.
• 3.3.10.1 Operational Description.
• A modulated signal at the desiredfrequency3802 is accepted and is transmitted over the desired medium, such as, but not limited to, over-the-air broadcast or point-to-point cable.
• 3.3.10.2 Structural Description.
• Thetransmission module3804 receives the signal at the desiredEM frequency3802. If it is intended to be broadcast over the air, the signal may be routed through an optional antenna interface and then to the antenna for broadcast. If it is intended for the signal to be transmitted over a cable from one point to another, the signal may be routed to an optional line driver and out through the cable. One skilled in the relevant art(s) will recognize that other transmission media may be used.
• 3.3.11 Other Implementations.
• The implementations described above are provided for purposes of illustration. These implementations are not intended to limit the invention. Other implementation embodiments are possible and covered by the invention, such as but not limited to software, software/hardware, and firmware implementations of the systems and components of the invention. Alternate implementations and embodiments, differing slightly or substantially from those described herein, will be apparent to persons skilled in the relevant art(s) based on the teachings contained herein. Such alternate implementations fall within the scope and spirit of the present invention.
• 4. Harmonic Enhancement.
• 4.1 High Level Description.
• This section (including its subsections) provides a high-level description of harmonic enhancement according to the present invention. In particular, pulse shaping is described at a high-level. Also, a structural implementation for achieving this process is described at a high-level. This structural implementation is described herein for illustrative purposes, and is not limiting. In particular, the process described in this section can be achieved using any number of structural implementations, one of which is described in this section. The details of such structural implementations will be apparent to persons skilled in the relevant art(s) based on the teachings contained herein.
• It is noted that some embodiments of the invention include harmonic enhancement, whereas other embodiments do not.
• 4.1.1 Operational Description.
• To better understand the generation and extraction of harmonics, and the purpose behind shaping the waveforms to enhance the harmonics, the following discussion of Fourier analysis as it applies to the present invention is offered.
• A discovery made by Baron Jean B. J. Fourier (1768-1830) showed that continuous and periodic waveforms are comprised of a plurality of sinusoidal components, called harmonics. More importantly, the frequency of these components are integer multiples of the frequency of the original waveform (called the fundamental frequency). The amplitude of each of these component waveforms depends on the shape of the original waveform. The derivations and proofs of Baron Fourier's analysis are well known to those skilled in the relevant art(s).
• The most basic waveform which is continuous and periodic is a sine wave. It has but one harmonic, which is at the fundamental frequency. This is also called the first harmonic. Since it only has one component, the amplitude of the harmonic component is equal to the amplitude of the original waveform, i.e., the sine wave itself. The sine wave is not considered to be “harmonically rich.”
• An impulse train is the other extreme case of a periodic waveform. Mathematically, it is considered to have zero width. The mathematical analysis in this case shows that there are harmonics at all multiples of the frequency of the impulse. That is, if the impulse has a frequency of F_i, then the harmonics are sinusoidal waves at 1·F_i, 2·F_i, 3·F_i, 4·F_i, etc. As the analysis also shows in this particular case, the amplitude of all of the harmonics are equal. This is indeed, a “harmonically rich” waveform, but is realistically impractical with current technology.
• A more typical waveform is a rectangular wave, which is a series of pulses. Each pulse will have a width (called a pulse width, or “τ”), and the series of pulses in the waveform will have a period (“T” which is the inverse of the frequency, i.e., T=1/F_r, where “F_r” is the fundamental frequency of the rectangular wave). One form of rectangular wave is the square wave, where the signal is at a first state (e.g., high) for the same amount of time that it is at the second state (e.g., low). That is, the ratio of the pulse width to period (τ/T) is 0.5. Other forms of rectangular waves, other than square waves, are typically referred to simply as “pulses,” and have τ/T<0.5 (i.e., the signal will be “high” for a shorter time than it is “low”). The mathematical analysis shows that there are harmonics at all of the multiples of the fundamental frequency of the signal. Thus, if the frequency of the rectangular waveform is Fr, then the frequency of the first harmonic is 1·F_r, the frequency of the second harmonic is 2·F_r, the frequency of the third harmonic is 3F_r, and so on. There are some harmonics for which the amplitude is zero. In the case of a square wave, for example, the “null points” are the even harmonics. For other values of τ/T, the “null points” can be determined from the mathematical equations. The general equation for the amplitude of the harmonics in a rectangular wave having an amplitude of A_pulseis as follows:
  Amplitude(n^thharmonic)=A_n={[A_pulse][(2/π)/n]sin[n·π·(τ/T)]}  Eq. 1
  Table6000 ofFIG. 60 shows the amplitudes of the first fifty harmonics for rectangular waves having six different τ/T ratios. The τ/T ratios are 0.5 (a square wave), 0.25, 0.10, 0.05, 0.01, and 0.005. (One skilled in the relevant art(s) will recognize that A_pulseis set to unity for mathematical comparison.) From this limited example, it can be seen that the ratio of pulse width to period is a significant factor in determining the relative amplitudes of the harmonics. Notice too, that for the case where τ/T=0.5 (i.e., a square wave), the relationship stated above (i.e., only odd harmonics are present) holds. Note that as τ/T becomes small (i.e., the pulse approaches an impulse), the amplitudes of the harmonics becomes substantially “flat.” That is, there is very little decrease in the relative amplitudes of the harmonics. One skilled in the relevant art(s) will understand how to select the desired pulse width for any given application based on the teachings contained herein. It can also be shown mathematically and experimentally that if a signal with a continuous and periodic waveform is modulated, that modulation is also present on every harmonic of the original waveform.
• From the foregoing, it can be seen how pulse width is an important factor in assuring that the harmonic waveform at the desired output frequency has sufficient amplitude to be useful without requiring elaborate filtering or unnecessary amplification.
• Another factor in assuring that the desired harmonic has sufficient amplitude is how theswitch2816 and3116 (FIGS. 28A and 31A) in theswitch module2802 and3102 responds to the control signal that causes the switch to close and to open (i.e., the modulatedoscillating signal2804 ofFIG. 28 and theoscillating signal3104 ofFIG. 31). In general, switches have two thresholds. In the case of a switch that is normally open, the first threshold is the voltage required to cause the switch to close. The second threshold is the voltage level at which the switch will again open. The convention used herein for ease of illustration and discussion (and not meant to be limiting) is for the case where the switch is closed when the control signal is high, and open when the control signal is low. It would be apparent to one skilled in the relevant art(s) that the inverse could also be used. Typically, these voltages are not identical, but they may be. Another factor is how rapidly the switch responds to the control input once the threshold voltage has been applied. The objective is for the switch to close and open such that the bias/reference signal is “crisply” gated. That is, preferably, the impedance through the switch must change from a high impedance (an open switch) to a low impedance (a closed switch) and back again in a very short time so that the output signal is substantially rectangular.
• It is an objective of this invention in the transmitter embodiment that the intelligence in the information signal is to be transmitted. That is, the information is modulated onto the transmitted signal. In the FM and PM modes, to achieve this objective, the information signal is used to modulate theoscillating signal2804. Theoscillating signal2804 then causes theswitch2816 to close and open. The information that is modulated onto theoscillating signal2804 must be faithfully reproduced onto the signal that is output from the switch circuit (i.e., the harmonically rich signal2814). For this to occur efficiently, in embodiments of the invention, theswitch2816 preferably closes and opens crisply so that the harmonicallyrich signal2814 changes rapidly from the bias/reference signal2806 (or3106) to ground2812 (or thesecond signal level2818 in the alternate embodiment). This rapid rise and fall time is desired so that the harmonicallyrich signal2814 will be “harmonically rich.” (In the case of AM, theoscillating signal3104 is not modulated, but the requirement for “crispness” still applies.)
• For theswitch2816 to close and open crisply, theoscillating signal2804 must also be crisp. If theoscillating signal2804 is sinusoidal, theswitch2816 will open and close when the threshold voltages are reached, but the pulse width of the harmonicallyrich signal2814 may not be as small as is needed to ensure the amplitude of the desired harmonic of the harmonicallyrich signal2814 is sufficiently high to allow transmission without elaborate filtering or unnecessary amplification. Also, in the embodiment wherein theswitch2816 is aGaAsFET2901, if theoscillating signal2804 that is connected to thegate2902 of the GaAsFET2901 (i.e., the signal that causes theswitch2816 to close and open) is a sinusoidal wave, theGaAsFET2901 will not crisply close and open, but will act more like an amplifier than a switch. (That is, it will conduct during the time that the oscillating signal is rising and falling below the threshold voltages, but will not be a “short.”) In order to make use of the benefits of a GaAsFET's capability to close and open at high frequencies, theoscillating signal2804 connected to thegate2902 preferably has a rapid rise and fall time. That is, it is preferably a rectangular waveform, and preferably has a pulse width to period ratio the same as the pulse width to period ratio of the harmonicallyrich signal2814.
• As stated above, if a signal with a continuous and periodic waveform is modulated, that modulation occurs on every harmonic of the original waveform. Thus, in the FM and PM modes, when the information is modulated onto theoscillating signal2804 and theoscillating signal2804 is used to cause theswitch2816 to close and open, the resulting harmonicallyrich signal2814 that is output from theswitch module2802 will also be modulated. If theoscillating signal2804 is crisp, theswitch2816 will close and open crisply, the harmonicallyrich signal2814 will be harmonically rich, and each of the harmonics of the harmonicallyrich signal2814 will have the information modulated on it.
• Because it is desired that theoscillating signal2804 be crisp, harmonic enhancement may be needed in some embodiments. Harmonic enhancement may also be called “pulse shaping” since the purpose is to shape theoscillating signal2804 into a string of pulses of a desired pulse width. If the oscillating signal is sinusoidal, harmonic enhancement will shape the sinusoidal signal into a rectangular (or substantially rectangular) waveform with the desired pulse width to period ratio. If theoscillating signal2804 is already a square wave or a pulse, harmonic enhancement will shape it to achieve the desired ratio of pulse width to period. This will ensure an efficient transfer of the modulated information through the switch.
• Three exemplary embodiments of harmonic enhancement are described below for illustrative purposes. However, the invention is not limited to these embodiments. Other embodiments will be apparent to persons skilled in the relevant art(s) based on the teachings contained herein.
• 4.1.2 Structural Description.
• The shape of theoscillating signal2804 causes theswitch2816 to close and open. The shape of theoscillating signal2804 and the selection of theswitch2816 will determine how quickly theswitch2816 closes and opens, and how long it stays closed compared to how long it stays open. This then will determine the “crispness” of the harmonicallyrich signal2814. (That is, whether the harmonicallyrich signal2814 is substantially rectangular, trapezoidal, triangular, etc.) As shown above, in order to ensure that the desired harmonic has the desired amplitude, the shape of theoscillating signal2804 should be substantially optimized.
• The harmonic enhancement module (HEM)4602 (FIG. 46) is also referred to as a “pulse shaper.” It “shapes” the oscillating signals2804 and3104 that drive theswitch modules2802 and3102 described in sections 3.3.6-3.3.6.2 and 3.3.7-3.3.7.2.Harmonic enhancement module4602 preferably transforms a continuous andperiodic waveform4604 into a string ofpulses4606. The string ofpulses4606 will have a period, “T,” determined by both the frequency of the continuous andperiodic waveform4604 and the design of the pulse shaping circuit within theharmonic enhancement module4602. Also, each pulse will have a pulse width, “τ,” determined by the design of the pulse shaping circuit. The period of the pulse stream, “T,” determines the frequency of the switch closing (the frequency being the inverse of the period), and the pulse width of the pulses, “τ,” determines how long the switch stays closed.
• In the embodiment described above in sections 3.3.6-3.3.6.2 (and 3.3.7-3.3.7.2), when the switch2816 (or3116) is open, the harmonically rich signal2814 (or3114) will have an amplitude substantially equal to the bias signal2806 (or reference signal3106). When the switch2816 (or3116) is closed, the harmonically rich signal2814 (or3114) will have an amplitude substantially equal to the potential ofsignal2812 or2818 (or3112 or3118) of the second input2810 (or3110) of the switch module2802 (or3102). Thus, for the case where the oscillating signal2804 (or3104) driving the switch module2802 (or3102) is substantially rectangular, the harmonically rich signal2814 (or3114) will have substantially the same frequency and pulse width as the shaped oscillating signal2804 (or3104) that drives the switch module2802 (or3102). This is true for those cases wherein the oscillating signal2804 (or3104) is a rectangular wave. One skilled in the relevant art(s) will understand that the term “rectangular wave” can refer to all waveforms that are substantially rectangular, including square waves and pulses.
• The purpose of shaping the signal is to control the amount of time that the switch2816 (or3116) is closed. As stated above, the harmonically rich signal2814 (or3114) has a substantially rectangular waveform. Controlling the ratio of the pulse width of the harmonically rich signal2814 (or3114) to its period will result in the shape of the harmonically rich signal2814 (or3114) being substantially optimized so that the relative amplitudes of the harmonics are such that the desired harmonic can be extracted without unnecessary and elaborate amplification and filtering.
• 4.2 Exemplary Embodiments.
• Various embodiments related to the method(s) and structure(s) described above are presented in this section (and its subsections). These embodiments are described herein for purposes of illustration, and not limitation. The invention is not limited to these embodiments. Alternate embodiments (including equivalents, extensions, variations, deviations, etc., of the embodiments described herein) will be apparent to persons skilled in the relevant art(s) based on the teachings contained herein. The invention is intended and adapted to include such alternate embodiments.
• 4.2.1 First Embodiment: When a Square Wave Feeds the Harmonic Enhancement Module to Create One Pulse per Cycle.
• 4.2.1.1 Operational Description.
• According to this embodiment, a continuousperiodic waveform4604 is received and a string ofpulses4606 is output. The continuousperiodic waveform4604 may be a square wave or any other continuous periodic waveform that varies from a value recognized as a “digital low” to a value recognized as a “digital high.” One pulse is generated per cycle of the continuous andperiodic waveform4604. The description given herein will be for the continuousperiodic waveform4604 that is a square wave, but one skilled in the relevant art(s) will appreciate that other waveforms may also be “shaped” intowaveform4606 by this embodiment.
• 4.2.1.2 Structural Description.
• In this first embodiment of aharmonic enhancement module4602, herein after referred to as apulse shaping circuit4602, a continuousperiodic waveform4604 that is a square wave is received by thepulse shaping circuit4602. Thepulse shaping circuit4602 is preferably comprised of digital logic devices that result in a string ofpulses4606 being output that has one pulse for every pulse in the continuousperiodic waveform4604, and preferably has a τ/T ratio less than 0.5.
• 4.2.2 Second Embodiment: When a Square Wave Feeds the Harmonic Enhancement Module to Create Two Pulses per Cycle.
• 4.2.2.1 Operational Description.
• In this embodiment, a continuousperiodic waveform4604 is received and a string ofpulses4606 is output. In this embodiment, there are two pulses output for every period of the continuousperiodic waveform4604. The continuousperiodic waveform4604 may be a square wave or any other continuous periodic waveform that varies from a value recognized as a “digital low” to a value recognized as a “digital high.” The description given herein will be for a continuousperiodic waveform4604 that is a square wave, but one skilled in the relevant art(s) will appreciate that other waveforms may also be “shaped” intowaveform4606 by this embodiment.
• 4.2.2.2 Structural Description.
• In this second embodiment of apulse shaping circuit4602, a continuousperiodic waveform4604 that is a square wave is received by thepulse shaping circuit4602. Thepulse shaping circuit4602 is preferably comprised of digital logic devices that result in a string ofpulses4606 being output that has two pulses for every pulse in the continuousperiodic waveform4604, and preferably has a τ/T ratio less than 0.5.
• 4.2.3 Third Embodiment: When Any Waveform Feeds the Module.
• 4.2.3.1 Operational Description.
• In this embodiment, a continuousperiodic waveform4604 of any shape is received and a string ofpulses4606 is output.
• 4.2.3.2 Structural Description.
• In this third embodiment of apulse shaping circuit4602, a continuousperiodic waveform4604 of any shape is received by thepulse shaping circuit4602. Thepulse shaping circuit4602 is preferably comprised of a series of stages, each stage shaping the waveform until it is substantially a string ofpulses4606 with preferably a τ/T ratio less than 0.5.
• 4.2.4 Other Embodiments.
• The embodiments described above are provided for purposes of illustration. These embodiments are not intended to limit the invention. Alternate embodiments, differing slightly or substantially from those described herein, will be apparent to persons skilled in the relevant art(s) based on the teachings contained herein. Such alternate embodiments fall within the scope and spirit of the present invention.
• 4.3 Implementation Examples.
• Exemplary operational and/or structural implementations related to the method(s), structure(s), and/or embodiments described above are presented in this section (and its subsections). These components and methods are presented herein for purposes of illustration, and not limitation. The invention is not limited to the particular examples of components and methods described herein. Alternatives (including equivalents, extensions, variations, deviations, etc., of those described herein) will be apparent to persons skilled in the relevant art(s) based on the teachings contained herein. Such alternatives fall within the scope and spirit of the present invention.
• 4.3.1 First Digital Logic Circuit.
• An exemplary implementation of the first embodiment described in sections 4.2.1-4.2.1.2 is illustrated inFIG. 39. In particular, the circuit shown inFIG. 39A is a typical circuit design for apulse shaping circuit4602 using digital logic devices. Also shown inFIGS. 39B-39D are representative waveforms at three nodes within the circuit. In this embodiment, pulse shaper3900 uses aninverter3910 and an ANDgate3912 to produce a string of pulses. An inverter, such asinverter3910, changes the sign of the input, and an AND gate, such as ANDgate3912, outputs a digital “high” when all of the input signals are digital “highs.” The input topulse shaper3900 iswaveform3902, and, for illustrative purposes, is shown here as a square wave. The output ofinverter3910 iswaveform3904, which is also a square wave. However, because of the circuitry of theinverter3910, there is a delay between the application of the input and the corresponding sign change of the output. Ifwaveform3902 starts “low,”waveform3904 will be “high” because it has been inverted byinverter3910. Whenwaveform3902 switches to “high,” ANDgate3912 will momentarily see two “high” signals, thus causing itsoutput waveform3906 to be “high.” Wheninverter3910 has inverted its input (waveform3902) and causedwaveform3904 to become “low,” ANDgate3912 will then see only one “high” signal, and theoutput waveform3906 will become “low.” Thus, theoutput waveform3906 will be “high” for only the period of time that bothwaveforms3902 and3904 are high, which is the time delay of theinverter3910. Accordingly, as is apparent fromFIGS. 39B-39D,pulse shaper3900 receives a square wave and generates a string of pulses, with one pulse generated per cycle of the square wave.
• 4.3.2 Second Digital Logic Circuit.
• An exemplary implementation of the second embodiment described in sections 4.2.2-4.2.2.2 is illustrated inFIG. 40. In particular, the circuit ofFIG. 40A is a typical circuit design for apulse shaping circuit4602 using digital logic devices. Also shown inFIGS. 40B-40D are representative waveforms at three nodes within the circuit. In this embodiment,pulse shaping circuit4000 uses aninverter4010 and an exclusive NOR (XNOR)gate4012. An XNOR, such asXNOR4012, outputs a digital “high” when both inputs are digital “highs” and when both signals are digital “lows.”Waveform4002, which is shown here as a square wave identical to that shown above aswaveform3902, begins in the “low” state. Therefore, the output ofinverter4010 will begin at the “high” state. Thus,XNOR gate4012 will see one “high” input and one “low” input, and itsoutput waveform4006 will be “low.” When waveform4002 changes to “high,”XNOR gate4012 will have two “high” inputs until thewaveform4004 switches to “low.” Because it sees two “high” inputs, itsoutput waveform4006 will be “high.” Whenwaveform4004 becomes “low,”XNOR gate4012 will again see one “high” input (waveform4002) and one “low” input (waveform4004). Whenwaveform4002 switches back to “low,”XNOR gate4012 will see two “low” inputs, and its output will become “high.” Following the time delay ofinverter4010,waveform4004 will change to “high,” andXNOR gate4012 will again see one “high” input (waveform4004) and one “low” input (waveform4002). Thus,waveform4006 will again switch to “low.” Accordingly, as is apparent fromFIGS. 40B-40D,pulse shaper4000 receives a square wave and generates a string of pulses, with two pulses generated per cycle of the square wave.
• 4.3.3 Analog Circuit.
• An exemplary implementation of the third embodiment described in sections 4.2.34.2.3.2 is illustrated inFIG. 41. In particular, the circuit shown inFIG. 41 is a typicalpulse shaping circuit4602 where aninput signal4102 is shown as a sine wave.Input signal4102 feeds thefirst circuit element4104, which in turn feeds the second, and so on. Typically, threecircuit elements4104 produce incrementally shapedwaveforms4120,4122, and4124 before feeding acapacitor4106. The output ofcapacitor4106 is shunted toground4110 through a resistor4108 and also feeds afourth circuit element4104. Anoutput signal4126 is a pulsed output, with a frequency that is a function of the frequency ofinput signal4102.
• An exemplary circuit forcircuit elements4104 is shown inFIG. 43.Circuit4104 is comprised of aninput4310, anoutput4312, fourFETs4302, twodiodes4304, and aresistor4306. One skilled in the relevant art(s) would recognize that other pulse shaping circuit designs could also be used without deviating from the scope and spirit of the invention.
• 4.3.4 Other Implementations.
• The implementations described above are provided for purposes of illustration. These implementations are not intended to limit the invention. Alternate implementations, differing slightly or substantially from those described herein, will be apparent to persons skilled in the relevant art(s) based on the teachings contained herein. Such alternate implementations fall within the scope and spirit of the present invention.
• 4.3.4.1 Multiple apertures
• In an alternate embodiment of the invention, a plurality of pulses are used to create multiple apertures from the switch module. The generation of the plurality of pulses can be through a number of techniques. The purpose of using multiple apertures is because of the optimizing effect it has on the amplitude of the harmonic content of the output waveform.
• Looking toFIG. 78, it can be seen that alocal oscillator7802 generates anoscillating signal7810. For ease of discussion, and not meant to be limiting, oscillatingsignal7810 is routed through apulse shaper7812 to create a string ofpulses7804. String ofpulses7804 is routed to a multipleaperture generation module7806. The output of multipleaperture generation module7806 is a string ofmultiple pulses7808.
• InFIG. 79, string ofpulses7804 is seen being accepted by multipleaperture generation module7806. String ofpulses7804 is then routed to one or more delays7904(i).FIG. 79 illustrates a first delay7904(a) that outputs a first delayed string of pulses7906(a). First delayed string of pulses7906(a) is substantially similar to string ofpulses7804, except that it is delayed in time by a desired period. String ofpulses7804 and first delayed string of pulses7906(a) are then routed to an “NOR” gate that outputs a string ofmultiple pulses7808 that has a pulse at every point in time that string ofpulses7804 has a pulse and at every point in time that first delayed string of pulses7906(a) has a pulse. Similarly, other delays such as a delay7904(n) also delay string ofpulses7804 by desired periods to create n^thdelayed string of pulses7906(n). When string ofpulses7804 and first through n^thdelayed strings of pulses7906(a)-7906(n) are combined by “NOR”gate7904, string ofmultiple pulses7808 is created having n+1 pulses for every cycle of string ofpulses7804.
• FIG. 80 illustrates apulse train8002 that is one pulse per cycle of string ofpulses7804. Similarly, apulse train8004 illustrates two pulses per cycle of string ofpulses7804; apulse train8006 illustrates three pulses per cycle of string ofpulses7804; apulse train8008 illustrates four pulses per cycle of string ofpulses7804; and apulse train8006 illustrates five pulses per cycle of string ofpulses7804. In this example, the desired output frequency is 900 MHz and the frequency of the string of pulses is 180 MHz. Thus, the fifth harmonic is the desired harmonic, and the optimum pulse width of the pulses in string ofpulses7804 is one-fifth of the period of string ofpulses7804. In this example, each of the additional pulses are separated from the leading pulse by a period of time equal to the pulse width, and, additionally, they each have a pulse width that is substantially equal to the pulse width of the pulses in string ofpulses7804.
• FIGS. 81 through 85 illustrate the advantages of using multiple apertures per cycle. InFIG. 81, the 900 MHz harmonic resulting form the use of a single pulse per cycle (i.e., pulse train8002) is shown by aspectrum8102. InFIG. 82, the 900 MHz harmonic resulting form the use of two pulses per cycle (i.e., pulse train8004) is shown by aspectrum8202. InFIG. 83, the 900 MHz harmonic resulting form the use of three pulses per cycle (i.e., pulse train8006) is shown by aspectrum8302. InFIG. 84, the 900 MHz harmonic resulting form the use of four pulses per cycle (i.e., pulse train8008) is shown by aspectrum8402. InFIG. 85, the 900 MHz harmonic resulting form the use of five pulses per cycle (i.e., pulse train8010) is shown by aspectrum8502.FIG. 86 illustrates the relative amplitude of these five spectra,8102,8202,8302,8402, and8502. As can be seen, the desired harmonic amplitude is increased and the undesired harmonics decreased as a function of the number of pulses per cycle. This increase in amplitude will be another consideration during the design of a transmitter.
• An alternate embodiment to improve the harmonic content of the output signal is shown incircuit8702 ofFIG. 87. A string of pulses as shown inFIG. 90 is phase shifted and inverted and the two strings of pulses are combined to create the bi-polar string of pulses shown inFIG. 89. The effect of the bi-polar string of pulses is to suppress the even harmonics and increase the amplitude of the odd harmonics. This ouput is shown inFIG. 88.
• 5. Amplifier Module.
• 5.1 High Level Description.
• This section (including its subsections) provides a high-level description of the amplifier module according to the present invention. In particular, amplification is described at a high-level. Also, a structural implementation for achieving signal amplification is described at a high-level. This structural implementation is described herein for illustrative purposes, and is not limiting. In particular, the process described in this section can be achieved using any number of structural implementations, one of which is described in this section. The details of such structural implementations will be apparent to persons skilled in the relevant art(s) based on the teachings contained herein.
• 5.1.1 Operational Description.
• Even though the present invention is intended to be used without requiring amplification, there may be circumstance when, in the embodiment of the present invention wherein it is being used as a transmitter, it may prove desirable to amplify the modulated signal before it is transmitted. In another embodiment of the invention wherein it is being used as a stable signal source for a frequency or phase comparator, it may also be desirable to amplify the resultant signal at the desired frequency.
• The requirement may come about for a number of reasons. A first may be that the bias/reference signal is too low to support the desired use. A second may be because the desired output frequency is very high relative to the frequency of the oscillating signal that controls the switch. A third reason may be that the shape of the harmonically rich signal is such that the amplitude of the desired harmonic is low.
• In the first case, recall that the amplitude of the bias/reference signal determines the amplitude of the harmonically rich signal which is present at the output of the switch circuit. (See sections 3.3.6-3.3.6.2 and 3.3.7-3.3.7.2.) Further recall that the amplitude of the harmonically rich signal directly impacts the amplitude of each of the harmonics. (See the equation in section 4.1, above.)
• In the second instance, if the frequency of the oscillating signal is relatively low compared to the desired output frequency of the up-converter, a high harmonic will be needed. As an example, if the oscillating signal is 60 MHz, and the desired output frequency is at 900 MHz, the 5^thharmonic will be needed. In the case where τ/T is 0.1, it can be seen from Table6000 ofFIG. 60 that the amplitude of the 5^thharmonic (A₁₅) is 0.0424, which is 21.5% of the amplitude of the first harmonic (A₁=0.197). There may be instances wherein this is insufficient for the desired use, and consequently it must be amplified.
• The third circumstance wherein the amplitude of the output may need to be amplified is when the shape of the harmonically rich signal in not “crisp” enough to provide harmonics with enough amplitude for the desired purpose. If, for example, the harmonically rich signal is substantially triangular, and given the example above where the oscillating signal is 60 MHz and the desired output signal is 900 MHz, the 15^thharmonic of the triangular wave is 0.00180. This is significantly lower than the amplitude of the 15^thharmonic of the “0.1” rectangular wave (shown above to be 0.0424) and can be mathematically shown to be 0.4% of the amplitude of the 1^stharmonic of the triangular wave (which is 0.405). Thus, in this example, the 1^stharmonic of the triangular wave has an amplitude that is larger than the amplitude of the 1^stharmonic of the “0.1” rectangular wave, but at the 15^thharmonic, the triangular wave is significantly lower than the “0.1” rectangular wave.
• Another reason that the desired harmonic may need to be amplified is that circuit elements such as the filter may cause attenuation in the output signal for which a designer may wish to compensate.
• The desired output signal can be amplified in a number of ways. One is to amplify the bias/reference signal to ensure that the amplitude of the harmonically rich wave form is high. A second is to amplify the harmonically rich waveform itself. A third is to amplify the desired harmonic only. The examples given herein are for illustrative purposes only and are not meant to be limiting on the present invention. Other techniques to achieve amplification of the desired output signal would be apparent to those skilled in the relevant art(s).
• 5.1.2 Structural Description.
• In one embodiment, a linear amplifier is used to amplify the bias/reference signal. In another embodiment, a linear amplifier is used to amplify the harmonically rich signal. And in yet another embodiment, a linear amplifier is used to amplify the desired output signal. Other embodiments, including the use of non-linear amplifiers, will be apparent to persons skilled in the relevant art(s).
• 5.2 Exemplary Embodiment.
• An embodiment related to the method(s) and structure(s) described above is presented in this section (and its subsections). This embodiment is described herein for purposes of illustration, and not limitation. The invention is not limited to this embodiment. Alternate embodiments (including equivalents, extensions, variations, deviations, etc., of the embodiment described herein) will be apparent to persons skilled in the relevant art(s) based on the teachings contained herein. The invention is intended and adapted to include such alternate embodiments.
• 5.2.1 Linear Amplifier.
• The exemplary linear amplifier described herein will be directed towards an amplifier composed of solid state electronic devices to be inserted in the circuit at one or more points. Other amplifiers suitable for use with the invention will be apparent to persons skilled in the relevant art(s). As shown inFIG. 47, anamplifier module4702 receives asignal requiring amplification4704 and outputs an amplifiedsignal4706. It would be apparent to one skilled in the relevant art(s) that a plurality of embodiments may be employed without deviating from the scope and intent of the invention described herein.
• 5.2.1.1 Operational Description.
• The desired output signal can be amplified in a number of ways. Such amplification as described in the section may be in addition to the techniques described above to enhance the shape of the harmonically rich signal by pulse shaping of the oscillating signal that causes the switch to close and open.
• 5.2.1.2 Structural Description.
• In one embodiment, a linear amplifier is placed between the bias/reference signal and the switch module. This will increase the amplitude of the bias/reference signal, and as a result, will raise the amplitude of the harmonically rich signal that is the output of the switch module. This will have the effect of not only raising the amplitude of the harmonically rich signal, it will also raise the amplitude of all of the harmonics. Some potential limitation of this embodiment are: the amplified bias/reference signal may exceed the voltage design limit for the switch in the switch circuit; the harmonically rich signal coming out of the switch circuit may have an amplitude that exceeds the voltage design limits of the filter; and/or unwanted distortion may occur from having to amplify a wide bandwidth signal.
• A second embodiment employs a linear amplifier between the switch module and the filter. This will raise the amplitude of the harmonically rich signal. It will also raise the amplitude of all of the harmonics of that signal. In an alternate implementation of this embodiment, the amplifier is tuned so that it only amplifies the desired frequencies. Thus, it acts both as an amplifier and as a filter. A potential limitation of this embodiment is that when the harmonically rich signal is amplified to raise a particular harmonic to the desired level the amplitude of the whole waveform is amplified as well. For example, in the case where the amplitude of the pulse, A_pulse, is equal to 1.0, to raise the 15^thharmonic from 0.0424 volts to 0.5 volts, the amplitude of each pulse in the harmonically rich signal, A_pulse, will increase from 1.0 to 11.8 volts. This may well exceed the voltage design limit of the filter.
• A third embodiment of an amplifier module will place a linear amplifier between the filter and the transmission module. This will only raise the amplitude of the desired harmonic, rather than the entire harmonically rich signal.
• Other embodiments, such as the use of non-linear amplifiers, will be apparent to one skilled in the relevant art(s), and will not be described herein.
• 5.2.2 Other Embodiments.
• The embodiments described above are provided for purposes of illustration. These embodiments are not intended to limit the invention. Alternate embodiments, differing slightly or substantially from those described herein, will be apparent to persons skilled in the relevant art(s) based on the teachings contained herein. Such alternate embodiments fall within the scope and spirit of the present invention.
• 5.3 Implementation Examples.
• Exemplary operational and/or structural implementations related to the method(s), structure(s), and/or embodiments described above are presented in this section (and its subsections). These components and methods are presented herein for purposes of illustration, and not limitation. The invention is not limited to the particular examples of components and methods described herein. Alternatives (including equivalents, extensions, variations, deviations, etc., of those described herein) will be apparent to persons skilled in the relevant art(s) based on the teachings contained herein. Such alternatives fall within the scope and spirit of the present invention.
• 5.3.1 Linear Amplifier.
• Although described below as if it were placed after the filter, the amplifier may also be placed before the filter without deviating from the intent of the invention.
• 5.3.1.1 Operational Description.
• According to embodiments of the invention, a linear amplifier receives a first signal at a first amplitude, and outputs a second signal at a second amplitude, wherein the second signal is proportional to the first signal. It is a objective of an amplifier that the information embedded onto the first signal waveform will also be embedded onto the second signal. Typically, it is desired that there be as little distortion in the information as possible.
• In a preferred embodiment, the second signal is higher in amplitude than the first signal, however, there may be implementations wherein it is desired that the second signal be lower than the first signal (i.e., the first signal will be attenuated).
• 5.3.1.2 Structural Description.
• The design and use of a linear amplifier is well known to those skilled in the relevant art(s). A linear amplifier may be designed and fabricated from discrete components, or it may be purchased “off the shelf.”
• Exemplary amplifiers are seen inFIG. 48. In the exemplary circuit diagram ofFIG. 48A, six transistors are used in a wideband amplifier. In the more basic exemplary circuit ofFIG. 48B, the amplifier is composed of one transistor, four resistors, and a capacitor. Those skilled in the relevant art(s) will recognize that numerous alternative designs may be used.
• 5.3.2 Other Implementations.
• The implementations described above are provided for purposes of illustration. These implementations are not intended to limit the invention. Alternate implementations, differing slightly or substantially from those described herein, will be apparent to persons skilled in the relevant art(s) based on the teachings contained herein. Such alternate implementations fall within the scope and spirit of the present invention.
• 6. Receiver/Transmitter System.
• The present invention is for a method and system for up-conversion of electromagnetic signals. In one embodiment, the invention is a source of a stable high frequency reference signal. In a second embodiment, the invention is a transmitter.
• This section describes a third embodiment. In the third embodiment, the transmitter of the present invention to be used in a receiver/transmitter communications system. This third embodiment may also be referred to as the communications system embodiment, and the combined receiver/transmitter circuit is referred to as a “transceiver.” There are several alternative enhancements to the communications systems embodiment.
• The following sections describe systems and methods related to exemplary embodiments for a receiver/transmitter system. It should be understood that the invention is not limited to the particular embodiments described below. Equivalents, extensions, variations, deviations, etc., of the following will be apparent to persons skilled in the relevant art(s) based on the teachings contained herein. Such equivalents, extensions, variations, deviations, etc., are within the scope and spirit of the present invention.
• 6.1 High Level Description.
• This section provides a high-level description of a receiver/transmitter system according to the present invention. The implementations are described herein for illustrative purposes, and are not limiting. In particular, any number of functional and structural implementations may be used, several of which are described in this section. The details of such functional and structural implementations will be apparent to persons skilled in the relevant art(s) based on the teachings contained herein.
• According to a first embodiment of the transmitter of the present invention is used with a traditional superheterodyne receiver. In this embodiment, the transmitter and the receiver can operate either in a full-duplex mode or in a half-duplex mode. In a full duplex mode, the transceiver can transmit and receive simultaneously. In the half-duplex mode, the transceiver can either transmit or receive, but cannot do both simultaneously. The full-duplex and the half-duplex modes will be discussed together for this embodiment.
• A second embodiment of the transceiver is for the transmitter of the present invention to be used with a universal frequency down conversion circuit being used as a receiver. In this embodiment the transceiver is used in a half-duplex mode.
• A third embodiment of the transceiver is for the transmitter of the present invention to be used with a universal frequency down conversion circuit, where the transceiver is used in a full-duplex mode.
• These embodiments of the transceiver are described below.
• 6.2 Exemplary Embodiments and Implementation Examples.
• Various embodiments related to the method(s) and structure(s) described above and exemplary operational and/or structural implementations related to those embodiments are presented in this section (and its subsections). These embodiments, components, and methods are described herein for purposes of illustration, and not limitation. The invention is not limited to these embodiments or to the particular examples of components and methods described herein. Alternatives (including equivalents, extensions, variations, deviations, etc., of those described herein) will be apparent to persons skilled in the relevant art(s) based on the teachings contained herein. Such alternatives fall within the scope and spirit of the present invention, and the invention is intended and adapted to include such alternatives.
• 6.2.1 First Embodiment: The Transmitter of the Present Invention Being Used in a Circuit with a Superheterodyne Receiver.
• A typical superheterodyne receiver is shown inFIG. 49. Anantenna4904 receives asignal4902. Typically,signal4902 is a radio frequency (RF) signal which is routed to afilter4910 and anamplifier4908. Thefilter4910 removes all but a frequency range that includes the desired frequency, and theamplifier4908 ensures that the signal strength will be sufficient for further processing. The output ofamplifier4908 is asignal4911.
• Alocal oscillator4914 generates anoscillating signal4916 which is combined withsignal4911 bymixer4912. The output ofmixer4912 is asignal4934 which is amplified by anamplifier4918 and filtered by afilter4920. The purpose ofamplifier4918 is to ensure that the strength ofsignal4934 is sufficient for further processing, and the purpose offilter4920 is to remove the undesired frequencies.
• A secondlocal oscillator4924 generates a secondoscillating signal4926 which is combined with the amplified/filteredsignal4934 by amixer4922. The output ofmixer4922 issignal4936. Again, anamplifier4928 and afilter4930 ensure that thesignal4936 is at the desired amplitude and frequency. The resulting signal is then routed todecoder4932 where the intelligence is extracted to obtainbaseband signal4938.
• Signal4934 is referred to as the first intermediate frequency (IF) signal, andsignal4936 is referred to as the second IF signal. Thus, the combination oflocal oscillator4914 andmixer4912 can be referred to as the first IF stage, and the combination oflocal oscillator4924 andmixer4922 can be referred to as the second IF stage.
• Exemplary frequencies for the circuit ofFIG. 49 are as follows.Signal4902 may be 900 MHz. Theoscillator signal4916 may be at 830 MHz, which will result in the frequency of the first IF signal,signal4934, being at 70 MHz. If the secondoscillating signal4926 is at 59 MHz, the second IF signal,signal4936, would be at 11 MHz. This frequency is typical of second IF frequencies.
• Other superheterodyne receiver configurations are well known and these can be used in the transceiver embodiments of the invention. Also, the exemplary frequencies mentioned above are provide for illustrative purposes only, and are not limiting.
• FIG. 50 shows a transmitter of the present invention in a transceiver circuit with a typical superheterodyne receiver. Accordingly,FIG. 50 illustrates an exemplary transceiver circuit of the invention. The transceiver includes areceiver module5001, which is implemented using any superheterodyne receiver configuration, and which is described above. The transceiver also includes atransmitter module5003, which is described below.
• In the FM and PM modes, aninformation signal5004 modulates an intermediate signal to produce theoscillating signal5002.Oscillating signal5002 is shaped by signal shaper5010 to produce a string of pulses5008 (see the discussion above regarding the benefits of harmonic enhancement). The string ofpulses5008 drives theswitch module5012. In the FM/PM modes, a bias/reference signal5006 is also received byswitch module5012. The output ofswitch module5012 is a harmonicallyrich signal5022. Harmonicallyrich signal5022 is comprised of a plurality of sinusoidal components, and is routed to a “high Q” filter that will remove all but the desired output frequency(ies). The desiredoutput frequency5024 is amplified by anamplifier5016 and routed to atransmission module5018 which outputs atransmission signal5026 which is routed to aduplexer5020. The purpose ofduplexer5020 is to permit a single antenna to be used simultaneously for both receiving and transmitting signals. The combination of receivedsignal4902 andtransmission signal5026 is aduplexed signal5028.
• In the AM mode, the same circuit ofFIG. 50 applies, except: (1) aninformation signal5030 replacesinformation signal5004; (2) bias/reference signal5006 is a function of theinformation signal5030; and (3) oscillatingsignal5002 is not modulated.
• This description is for the full-duplex mode of the transceiver wherein the transmitting portion of the communications system is a separate circuit than the receiver portion. A possible embodiment of a half-duplex mode is described below.
• Alternate embodiments of the transceiver are possible. For example,FIGS. 51A through 51D illustrate an embodiment of the transceiver wherein it may be desired, for cost or other considerations, for an oscillator to be shared by both the transmitter portion and the receiver portion of the circuit. To do this, a trade off must be made in selecting the frequency of the oscillator. InFIG. 51A, alocal oscillator5104 generates anoscillating signal5106 which is mixed withsignal4911 to generate a first IFsignal5108. Alocal oscillator5110 generates a secondoscillating signal5112 which is mixed with the first IFsignal5108 to generate a second IFsignal5114. For the example herein, the frequencies of theoscillating signals5106 and5112 will be lower than the frequencies ofsignal4911 and first IFsignal5108, respectively. (One skilled in the relevant art(s) will recognize that, because themixers4912 and4922 create both the sum and the difference of the signals they receive, the oscillator frequencies could be higher than the signal frequencies.)
• As described in the example above, a typical second IF frequency is 11 MHz. The selection of this IF frequency is less flexible than is the selection of the first IF frequency, since the second IF frequency is routed to a decoder where the signal is demodulated and decoded. Typically, demodulators and decoders are designed to receive signals at a predetermined, fixed frequency, e.g., 11 MHz. If this is the case, the combination of the first IFsignal5108 and the secondoscillating signal5112 must generate a second IF signal with a second IF frequency of 11 MHz. Recall that the receivedsignal4902 was 900 MHz in the example above. To achieve the second IF signal frequency of 11 MHz, the frequencies of theoscillating signals4916 and4926 were set at 830 MHz and 59 MHz. Before setting the frequencies of theoscillating signals5106 and5112, the desired frequency of the transmitted signal must be determined. If it, too, is 900 MHz, then the frequency of the oscillating signal that causes the switch in the present invention to open and close must be a “sub-harmonic” of 900 MHz. That is, it must be the quotient of 900 MHz divided by an integer. (In other words, 900 MHz must be a harmonic of the oscillating signal that drives the switch.) The table below is a list of some of the sub-harmonics of 900 MHz:

  	sub-harmonic	frequency
  	1st	900MHz
  	2nd	450
  	3rd	300
  	4th	225
  	5th	180
  	10th	90
  	15th	60

  
  Recall that the frequency of the secondoscillating signal4926 inFIGS. 49 and 50 was 59 MHz. Notice that the frequency of the 15^thsub-harmonic is 60 MHz. If the frequency ofoscillating signal5112 ofFIG. 51 were set at 60 MHz, it could also be used as the oscillating signal to operate the switches inswitch module5126 ofFIG. 51B andswitch module5136 ofFIG. 51C. If this were done, the frequency of the first IF signal would be 71 MHz (rather than 70 MHz in the previous example of a stand-alone receiver), as indicated below:$\begin{array}{c}\mathrm{First}\mathrm{IF}\mathrm{frequency}=\mathrm{Second}\mathrm{IF}\mathrm{frequency}+\mathrm{Second}\mathrm{oscillating}\\ \mathrm{frequency}\\ =11\mathrm{MHz}+60\mathrm{MHz}\\ =71\mathrm{MHz}\end{array}$
  The frequency of the firstoscillating signal5106 can be determined from the values of the first IF frequency and the frequency of the receivedsignal4902. In this example, the frequency of the received signal is 900 MHz and the frequency of the first IF signal is 71 MHz. Therefore, the frequency of the firstoscillating signal5106 must be 829 MHz, as indicated below:$\begin{array}{c}\mathrm{First}\mathrm{oscillating}\mathrm{frequency}=\mathrm{Freq}\mathrm{of}\mathrm{received}\mathrm{signal}-\\ F\mathrm{irst}\mathrm{IF}\mathrm{freq}\\ =900\mathrm{MHz}-71\mathrm{MHz}\\ =829\mathrm{MHz}\end{array}$
  Thus the frequencies of theoscillating signals5106 and5112 are 829 MHz and 60 MHz, respectively.
• InFIG. 51B, the PM embodiment is shown. The secondoscillating signal5112 is routed to aphase modulator5122 where it is modulated by theinformation signal5120 to generate aPM signal5132.PM signal5132 is routed to aharmonic enhancement module5124 to create a string ofpulses5133. The string ofpulses5133 is also a phase modulated signal and is used to cause the switch inswitch module5126 to open and close. Also enteringswitch module5126 is abias signal5128. The output ofswitch module5126 is a harmonicallyrich signal5134.
• InFIG. 51C, the AM embodiment is shown. The secondoscillating signal5112 directly enters theharmonic enhancement module5124 to create a string ofpulses5138. String of pulses5138 (not modulated in this embodiment) then enters aswitch module5136 where it causes a switch to open and close. Also enteringswitch module5136 is areference signal5140. Reference signal is created by summingmodule5130 by combininginformation signal5120 withbias signal5128. It is well known to those skilled in the relevant art(s) that theinformation signal5120 may be used as the reference signal without being combined with thebias signal5128. The output ofswitch module5136 is a harmonicallyrich signal5134.
• The scope of the invention includes an FM embodiment wherein theoscillator5110 of the receiver circuit is used as a source for an oscillating signal for the transmitter circuit. In the embodiments discussed above, the FM embodiment requires a voltage controlled oscillator (VCO) rather than a simple local oscillator. There are circuit designs that would be apparent to those skilled in the relevant art(s) based on the discussion contained herein, wherein a VCO is used in place of a local oscillator in the receiver circuit.
• InFIG. 51D, the harmonicallyrich signal5134 is filtered by afilter5142, which removes all but the desiredoutput frequency5148. The desiredoutput frequency5148 is amplified byamplifier module5146 and routed totransmission module5150. The output oftransmission module5150 is atransmission signal5144.Transmission signal5144 is then routed to theantenna4904 for transmission.
• Those skilled in the relevant art(s) will understand that there are numerous combinations of oscillator frequencies, stages, and circuits that will meet the scope and intent of this invention. Thus, the description included herein is for illustrative purposes only and not meant to be limiting.
• 6.2.2 Second Embodiment: The Transmitter of the Present Invention Being Used with a Universal Frequency Down-Converter in a Half-Duplex Mode.
• An exemplary receiver using universal frequency down conversion techniques is shown inFIG. 52 and described in section 6.3, below. Anantenna5202 receives an electromagnetic (EM)signal5220.EM signal5220 is routed through acapacitor5204 to a first terminal of aswitch5210. The other terminal ofswitch5210 is connected toground5212 in this exemplary embodiment. Alocal oscillator5206 generates anoscillating signal5228 which is routed through apulse shaper5208. The result is a string ofpulses5230. The selection of theoscillator5206 and the design of thepulse shaper5208 control the frequency and pulse width of the string ofpulses5230. The string ofpulses5230 control the opening and closing ofswitch5210. As a result of the opening and closing ofswitch5210, a down convertedsignal5222 results. Down convertedsignal5222 is routed through anamplifier5214 and afilter5216, and a filteredsignal5224 results. In a preferred embodiment, filteredsignal5224 is at baseband, and adecoder5218 may only be needed to convert digital to analog or to remove encryption before outputting the baseband information signal. This then is a universal frequency down conversion receiver operating in a direct down conversion mode, in that it receives theEM signal5220 and down converts it tobaseband signal5226 without requiring an IF or a demodulator. In an alternate embodiment, the filteredsignal5224 may be at an “offset” frequency. That is, it is at an intermediate frequency, similar to that described above for the second IF signal in a typical superheterodyne receiver. In this case, thedecoder5218 would be used to demodulate the filtered signal so that it could output abaseband signal5226.
• An exemplary transmitter using the present invention is shown inFIG. 53. In the FM and PM embodiments, aninformation signal5302 modulates anoscillating signal5306 which is routed to apulse shaping circuit5310 which outputs a string ofpulses5311. The string ofpulses5311 controls the opening and closing of theswitch5312. One terminal ofswitch5312 is connected toground5314, and the second terminal ofswitch5312 is connected through aresistor5330 to a bias/reference signal5308. In the FM and PM modes, bias/reference signal5308 is preferably a non-varying signal, often referred to simply as the bias signal. In the AM mode, theoscillating signal5306 is not modulated, and the bias/reference signal is a function of theinformation signal5304. In one embodiment,information signal5304 is combined with a bias voltage to generate thereference signal5308. In an alternate embodiment, theinformation signal5304 is used without being combined with a bias voltage. Typically, in the AM mode, this bias/reference signal is referred to as the reference signal to distinguish it from the bias signal used in the FM and PM modes. The output ofswitch5312 is a harmonicallyrich signal5316 which is routed to a “high Q” filter which removes the unwanted frequencies that exist as harmonic components of harmonicallyrich signal5316. Desiredfrequency5320 is amplified byamplifier module5322 and routed totransmission module5324 which outputs atransmission signal5326. Transmission signal is output byantenna5328 in this embodiment.
• For the FM and PM modulation modes,FIGS. 54A, 54B, and54C show the combination of the present invention of the transmitter and the universal frequency down-conversion receiver in the half-duplex mode according to an embodiment of the invention. That is, the transceiver can transmit and receive, but it cannot do both simultaneously. It uses asingle antenna5402, asingle oscillator5444/5454 (depending on whether the transmitter is in the FM or PM modulation mode), asingle pulse shaper5438, and asingle switch5420 to transmit and to receive. In the receive function, “Receiver/transmitter” (R/T) switches5406,5408, and5446/5452 (FM or PM) would all be in the receive position, designated by (R). Theantenna5402 receives anEM signal5404 and routes it through acapacitor5407. In the FM modulation mode, oscillatingsignal5436 is generated by a voltage controlled oscillator (VCO)5444. Because the transceiver is performing the receive function,switch5446 connects the input to theVCO5444 toground5448. Thus,VCO5444 will operate as if it were a simple oscillator. In the PM modulation mode, oscillatingsignal5436 is generated bylocal oscillator5454 which is routed throughphase modulator5456. Since the transceiver is performing the receive function,switch5452 is connected toground5448, and there is no modulating input to phase modulator. Thus,local oscillator5454 andphase modulator5456 operate as if they were a simple oscillator. One skilled in the relevant art(s) will recognize based on the discussion contained herein that there are numerous embodiments wherein anoscillating signal5436 can be generated to control theswitch5420.
• Oscillating signal5436 is shaped by pulse shaper5438 to produce a string ofpulses5440. The string ofpulses5440 cause theswitch5420 to open and close. As a result of the switch opening and closing, a down convertedsignal5409 is generated. The down convertedsignal5409 is amplified and filtered to create a filteredsignal5413. In an embodiment, filteredsignal5413 is at baseband and, as a result of the down conversion, is demodulated. Thus, adecoder5414 may not be required except to convert digital to analog or to decrypt the filteredsignal5413. In an alternate embodiment, the filteredsignal5413 is at an “offset” frequency, so that thedecoder5414 is needed to demodulate the filtered signal and create a demodulated baseband signal.
• When the transceiver is performing the transmit function, the R/T switches5406,5408, and5446/5452 (FM or PM) are in the (T) position. In the FM modulation mode, aninformation signal5450 is connected byswitch5446 toVCO5444 to create a frequency modulatedoscillating signal5436. In the PMmodulation mode switch5452 connectsinformation signal5450 to thephase modulator5456 to create a phase modulatedoscillating signal5436.Oscillation signal5436 is routed through pulse shaper5438 to create a string ofpulses5440 which inturn cause switch5420 to open and close. One terminal ofswitch5420 is connected toground5442 and the other is connected through switch R/T5408 andresistor5423 to abias signal5422. The result is a harmonicallyrich signal5424 which is routed to a “high Q”filter5426 which removes the unwanted frequencies that exist as harmonic components of harmonicallyrich signal5424. Desiredfrequency5428 is amplified byamplifier module5430 and routed totransmission module5432 which outputs atransmission signal5434. Again, because the transceiver is performing the transmit function, R/T switch5406 connects the transmission signal to theantenna5402.
• In the AM modulation mode, the transceiver operates in the half duplex mode as shown inFIG. 55. The only distinction between this modulation mode and the FM and PM modulation modes described above, is that theoscillating signal5436 is generated by alocal oscillator5502, and theswitch5420 is connected through the R/T switch5408 andresistor5423 to areference signal5506.Reference signal5506 is generated wheninformation signal5450 andbias signal5422 are combined by a summingmodule5504. It is well known to those skilled in the relevant art(s) that theinformation signal5450 may be used as thereference signal5506 without being combined with thebias signal5422, and may be connected directly (throughresistor5423 and R/T switch5408) to theswitch5420.
• 6.2.3 Third Embodiment: The Transmitter of the Present Invention Being Used with a Universal Frequency Down Converter in a Full-Duplex Mode.
• The full-duplex mode differs from the half-duplex mode in that the transceiver can transmit and receive simultaneously. Referring toFIG. 56, to achieve this, the transceiver preferably uses a separate circuit for each function. Aduplexer5604 is used in the transceiver to permit the sharing of anantenna5602 for both the transmit and receive functions.
• The receiver function performs as follows. Theantenna5602 receives anEM signal5606 and routes it through acapacitor5607 to one terminal of aswitch5626. The other terminal ofswitch5626 is connected toground5628, and the switch is driven as a result of a string ofpulses5624 created bylocal oscillator5620 andpulse shaper5622. The opening and closing ofswitch5626 generates a down convertedsignal5614. Down convertedsignal5614 is routed through aamplifier5608 and afilter5610 to generate filteredsignal5616. Filteredsignal5616 may be at baseband and be demodulated or it may be at an “offset” frequency. If filteredsignal5616 is at an offset frequency,decoder5612 will demodulate it to create thedemodulated baseband signal5618. In a preferred embodiment, however, the filteredsignal5616 will be a demodulated baseband signal, anddecoder5612 may not be required except to convert digital to analog or to decrypt filteredsignal5616. This receiver portion of the transceiver can operate independently from the transmitter portion of the transceiver.
• The transmitter function is performed as follows. In the FM and PM modulation modes, aninformation signal5648 modulates anoscillating signal5630. In the AM modulation mode, theoscillating signal5630 is not modulated. The oscillating signal is shaped bypulse shaper5632 and a string ofpulses5634 is created. This string ofpulses5634 causes aswitch5636 to open and close. One terminal ofswitch5636 is connected toground5638, and the other terminal is connected through aresistor5647 to a bias/reference signal5646. In the FM and PM modulation modes, bias/reference signal5646 is referred to as abias signal5646, and it is substantially non-varying. In the AM modulation mode, aninformation signal5650 may be combined with the bias signal to create what is referred to as thereference signal5646. Thereference signal5646 is a function of theinformation signal5650. It is well known to those skilled in the relevant art(s) that theinformation signal5650 may be used as the bias/reference signal5646 directly without being summed with a bias signal. A harmonicallyrich signal5652 is generated and is filtered by a “high Q”filter5640, thereby producing a desiredsignal5654. The desiredsignal5654 is amplified byamplifier5642 and routed totransmission module5644. The output oftransmission module5644 istransmission signal5656.Transmission signal5656 is routed toduplexer5604 and then transmitted byantenna5602. This transmitter portion of the transceiver can operate independently from the receiver portion of the transceiver.
• Thus, as described above, the transceiver embodiment the present invention as shown inFIG. 56 can perform full-duplex communications in all modulation modes.
• 6.2.4 Other Embodiments and Implementations.
• Other embodiments and implementations of the receiver/transmitter of the present invention would be apparent to one skilled in the relevant art(s) based on the discussion herein.
• The embodiments and implementations described above are provided for purposes of illustration. These embodiments and implementations are not intended to limit the invention. Alternatives, differing slightly or substantially from those described herein, will be apparent to persons skilled in the relevant art(s) based on the teachings contained herein. Such alternate embodiments and implementations fall within the scope and spirit of the present invention.
• 6.3 Summary Description of Down-conversion Using a Universal Frequency Translation Module.
• The following discussion describes down-converting using a Universal Frequency Translation Module. The down-conversion of an EM signal by aliasing the EM signal at an aliasing rate is fully described in co-pending U.S. patent application entitled “Method and System for Down-converting an Electromagnetic Signal,” Application Ser. No. ______, Attorney Docket Number 1744.0010000, the full disclosure of which is incorporated herein by reference. A relevant portion of the above mentioned patent application is summarized below to describe down-converting an input signal to produce a down-converted signal that exists at a lower frequency or a baseband signal.
• FIG. 64A illustrates analiasing module6400 for down-conversion using a universal frequency translation (UFT)module6402 which down-converts anEM input signal6404. In particular embodiments,aliasing module6400 includes aswitch6408 and acapacitor6410. The electronic alignment of the circuit components is flexible. That is, in one implementation, theswitch6408 is in series withinput signal6404 andcapacitor6410 is shunted to ground (although it may be other than ground in configurations such as differential mode). In a second implementation (seeFIG. 64A-1), thecapacitor6410 is in series with theinput signal6404 and theswitch6408 is shunted to ground (although it may be other than ground in configurations such as differential mode).Aliasing module6400 withUFT module6402 can be easily tailored to down-convert a wide variety of electromagnetic signals using aliasing frequencies that are well below the frequencies of theEM input signal6404.
• In one implementation,aliasing module6400 down-converts theinput signal6404 to an intermediate frequency (IF) signal. In another implementation, thealiasing module6400 down-converts theinput signal6404 to a demodulated baseband signal. In yet another implementation, theinput signal6404 is a frequency modulated (FM) signal, and thealiasing module6400 down-converts it to a non-FM signal, such as a phase modulated (PM) signal or an amplitude modulated (AM) signal. Each of the above implementations is described below.
• In an embodiment, thecontrol signal6406 includes a train of pulses that repeat at an aliasing rate that is equal to, or less than, twice the frequency of theinput signal6404 In this embodiment, thecontrol signal6406 is referred to herein as an aliasing signal because it is below the Nyquist rate for the frequency of theinput signal6404. Preferably, the frequency ofcontrol signal6406 is much less than theinput signal6404.
• The train ofpulses6418 as shown inFIG. 64D controls theswitch6408 to alias theinput signal6404 with thecontrol signal6406 to generate a down-convertedoutput signal6412. More specifically, in an embodiment,switch6408 closes on a first edge of eachpulse6420 ofFIG. 64D and opens on a second edge of each pulse. When theswitch6408 is closed, theinput signal6404 is coupled to thecapacitor6410, and charge is transferred from the input signal to thecapacitor6410. The charge stored during successive pulses forms down-convertedoutput signal6412.
• Exemplary waveforms are shown inFIGS. 64B-64F.
• FIG. 64B illustrates an analog amplitude modulated (AM)carrier signal6414 that is an example ofinput signal6404. For illustrative purposes, inFIG. 64C, an analog AMcarrier signal portion6416 illustrates a portion of the analogAM carrier signal6414 on an expanded time scale. The analog AMcarrier signal portion6416 illustrates the analogAM carrier signal6414 from time to t₀time t₁.
• FIG. 64D illustrates anexemplary aliasing signal6418 that is an example ofcontrol signal6406.Aliasing signal6418 is on approximately the same time scale as the analog AMcarrier signal portion6416. In the example shown inFIG. 64D, thealiasing signal6418 includes a train ofpulses6420 having negligible apertures that tend towards zero (the invention is not limited to this embodiment, as discussed below). The pulse aperture may also be referred to as the pulse width as will be understood by those skilled in the art(s). Thepulses6420 repeat at an aliasing rate, or pulse repetition rate ofaliasing signal6418. The aliasing rate is determined as described below, and further described in co-pending U.S. patent application entitled “Method and System for Down-converting an Electromagnetic Signal,” Application Ser. No. ______, Attorney Docket Number 1744.0010000.
• As noted above, the train of pulses6420 (i.e., control signal6406) control theswitch6408 to alias the analog AM carrier signal6416 (i.e., input signal6404) at the aliasing rate of thealiasing signal6418. Specifically, in this embodiment, theswitch6408 closes on a first edge of each pulse and opens on a second edge of each pulse. When theswitch6408 is closed,input signal6404 is coupled to thecapacitor6410, and charge is transferred from theinput signal6404 to thecapacitor6410. The charge transferred during a pulse is referred to herein as an under-sample. Exemplary under-samples6422 form down-converted signal portion6424 (FIG. 64E) that corresponds to the analog AM carrier signal portion6416 (FIG. 64C) and the train of pulses6420 (FIG. 64D). The charge stored during successive under-samples ofAM carrier signal6414 form the down-converted signal6424 (FIG. 64E) that is an example of down-converted output signal6412 (FIG. 64A). InFIG. 64F ademodulated baseband signal6426 represents the demodulatedbaseband signal6424 after filtering on a compressed time scale. As illustrated, down-convertedsignal6426 has substantially the same “amplitude envelope” asAM carrier signal6414. Therefore,FIGS. 64B-64F illustrate down-conversion ofAM carrier signal6414.
• The waveforms shown inFIGS. 64B-64F are discussed herein for illustrative purposes only, and are not limiting. Additional exemplary time domain and frequency domain drawings, and exemplary methods and systems of the invention relating thereto, are disclosed in co-pending U.S. patent application entitled “Method and System for Down-converting an Electromagnetic Signal,” Application Ser. No. ______, Attorney Docket Number 1744.0010000.
• The aliasing rate ofcontrol signal6406 determines whether theinput signal6404 is down-converted to an IF signal, down-converted to a demodulated baseband signal, or down-converted from an FM signal to a PM or an AM signal. Generally, relationships between theinput signal6404, the aliasing rate of thecontrol signal6406, and the down-convertedoutput signal6412 are illustrated below:
  (Freq. of input signal6404)=n·(Freq. of control signal6406)±(Freq. of down-converted output signal6412)
  For the examples contained herein, only the “+” condition will be discussed. The value of n represents a harmonic or sub-harmonic of input signal6404 (e.g., n=0.5, 1, 2, 3, . . . ).
• When the aliasing rate ofcontrol signal6406 is off-set from the frequency ofinput signal6404, or off-set from a harmonic or sub-harmonic thereof,input signal6404 is down-converted to an IF signal. This is because the under-sampling pulses occur at different phases of subsequent cycles ofinput signal6404. As a result, the under-samples form a lower frequency oscillating pattern. If theinput signal6404 includes lower frequency changes, such as amplitude, frequency, phase, etc., or any combination thereof, the charge stored during associated under-samples reflects the lower frequency changes, resulting in similar changes on the down-converted IF signal. For example, to down-convert a 901 MHz input signal to a 1 MHz IF signal, the frequency of thecontrol signal6406 would be calculated as follows:
  (Freq_input−Freq_IF)_n=Freq_control
  (901 MHz−1 MHz)/n=900/n
  For n=0.5, 1, 2, 3, 4, etc., the frequency of thecontrol signal6406 would be substantially equal to 1.8 GHz, 900 MHz, 450 MHz, 300 MHz, 225 MHz, etc.
• Exemplary time domain and frequency domain drawings, illustrating down-conversion of analog and digital AM, PM and FM signals to IF signal, and exemplary methods and systems thereof, are disclosed in co-pending U.S. patent application entitled “Method and System for Down-converting an Electromagnetic Signal,” Application Ser. No. ______, Attorney Docket Number 1744.0010000.
• Alternatively, when the aliasing rate of thecontrol signal6406 is substantially equal to the frequency of theinput signal6404, or substantially equal to a harmonic or sub-harmonic thereof,input signal6404 is directly down-converted to a demodulated baseband signal. This is because, without modulation, the under-sampling pulses occur at the same point of subsequent cycles of theinput signal6404. As a result, the under-samples form a constant output baseband signal. If theinput signal6404 includes lower frequency changes, such as amplitude, frequency, phase, etc., or any combination thereof, the charge stored during associated under-samples reflects the lower frequency changes, resulting in similar changes on the demodulated baseband signal. For example, to directly down-convert a 900 MHz input signal to a demodulated baseband signal (i.e., zero IF), the frequency of thecontrol signal6406 would be calculated as follows:
  (Freq_input−Freq_IF)/n=Freq_control
  (900 MHz−0 MHz)/n=900 MHz/n
  For n=0.5, 1, 2, 3, 4, etc., the frequency of thecontrol signal6406 should be substantially equal to 1.8 GHz, 900 MHz, 450 MHz, 300 MHz, 225 MHz, etc.
• Exemplary time domain and frequency domain drawings, illustrating direct down-conversion of analog and digital AM and PM signals to demodulated baseband signals, and exemplary methods and systems thereof, are disclosed in the co-pending U.S. patent application entitled “Method and System for Down-converting an Electromagnetic Signal,” Application Ser. No. ______, Attorney Docket Number 1744.0010000.
• Alternatively, to down-convert an input FM signal to a non-FM signal, a frequency within the FM bandwidth must be down-converted to baseband (i.e., zero IF). As an example, to down-convert a frequency shift keying (FSK) signal (a sub-set of FM) to a phase shift keying (PSK) signal (a subset of PM), the mid-point between a lower frequency F₁and an upper frequency F₂(that is, [(F₁+F₂)÷2]) of the FSK signal is down-converted to zero IF. For example, to down-convert an FSK signal having F₁equal to 899 MHz and F₂equal to 901 MHz, to a PSK signal, the aliasing rate of thecontrol signal6406 would be calculated as follows:$\begin{array}{c}\mathrm{Frequency}\mathrm{of}\mathrm{the}\mathrm{input}=\left({\mathrm{<figure-callout\; label="F"\; filenames="US20050215207A1-20050929-D00005.png,US20050215207A1-20050929-D00006.png"\; state="\{\{state\}\}">F</figure-callout>}}_1+F_2\right)÷2\\ =\left(899\mathrm{MHz}+901\mathrm{MHz}\right)÷2\\ =900\mathrm{MHz}\end{array}$
  Frequency of the down-converted signal=0 (i.e., baseband)
  (Freq_input−Freq_IF)/n=Freq_control
  (900 MHz−0 MHz)/n=900 MHz/n
  For n=0.5, 1, 2, 3, etc., the frequency of thecontrol signal6406 should be substantially equal to 1.8 GHz, 900 MHz, 450 MHz, 300 MHz, 225 MHz, etc. The frequency of the down-converted PSK signal is substantially equal to one half the difference between the lower frequency F₁and the upper frequency F₂.
• As another example, to down-convert a FSK signal to an amplitude shift keying (ASK) signal (a subset of AM), either the lower frequency F₁or the upper frequency F₂of the FSK signal is down-converted to zero IF. For example, to down-convert an FSK signal having F₁equal to 900 MHz and F₂equal to 901 MHz, to an ASK signal, the aliasing rate of thecontrol signal6406 should be substantially equal to:
  (900 MHz−0 MHz)/n=900 MHz/n, or
  (901 MHz−0 MHz)/n=901 MHz/n.
  For the former case of 900 MHz/n, and for n=0.5, 1, 2, 3, 4, etc., the frequency of thecontrol signal6406 should be substantially equal to 1.8 GHz, 900 MHz, 450 MHz, 300 MHz, 225 MHz, etc. For the latter case of 901 MHz/n, and for n=0.5, 1, 2, 3, 4, etc., the frequency of thecontrol signal6406 should be substantially equal to 1.802 GHz, 901 MHz, 450.5 MHz, 300.333 MHz, 225.25 MHz, etc. The frequency of the down-converted AM signal is substantially equal to the difference between the lower frequency F₁and the upper frequency F₂(i.e., 1 MHz).
• Exemplary time domain and frequency domain drawings, illustrating down-conversion of FM signals to non-FM signals, and exemplary methods and systems thereof, are disclosed in the co-pending U.S. patent application entitled “Method and System for Down-converting an Electromagnetic Signal,” Application Ser. No. ______, Attorney Docket Number 1744.0010000.
• In an embodiment, the pulses of thecontrol signal6406 have negligible apertures that tend towards zero. This makes the UFT module6402 a high input impedance device. This configuration is useful for situations where minimal disturbance of the input signal may be desired.
• In another embodiment, the pulses of thecontrol signal6406 have non-negligible apertures that tend away from zero. This makes the UFT module6402 a lower input impedance device. This allows the lower input impedance of theUFT module6402 to be substantially matched with a source impedance of theinput signal6404. This also improves the energy transfer from theinput signal6404 to the down-convertedoutput signal6412, and hence the efficiency and signal to noise (s/n) ratio ofUFT module6402.
• Exemplary systems and methods for generating and optimizing thecontrol signal6406 and for otherwise improving energy transfer and s/n ratio, are disclosed in the co-pending U.S. patent application entitled “Method and System for Down-converting an Electromagnetic Signal,” Application Ser. No. ______, Attorney Docket Number 1744.0010000.
• 7. Designing a Transmitter According to an Embodiment of the Present Invention.
• This section (including its subsections) provides a high-level description of an exemplary process to be used to design a transmitter according to an embodiment of the present invention. The techniques described herein are also applicable to designing a frequency up-converter for any application, and for designing the applications themselves. The descriptions are contained herein for illustrative purposes and are not limiting. Alternatives (including equivalents, extensions, variations, deviations, etc., of those described herein) will be apparent to persons skilled in the relevant art(s) based on the teachings contained herein. Such alternatives fall within the scope and spirit of the present invention, and the invention is intended and adapted to include such alternative.
• The discussion herein describes an exemplary process to be used to design a transmitter according to an embodiment of the present invention. An exemplary circuit for a transmitter of the present invention operating in the FM embodiment is shown inFIG. 57A. Likewise,FIG. 57B illustrates the transmitter of the present invention operating in the PM embodiment, andFIG. 57C shows the transmitter of the present invention operating in the AM embodiment. These circuits have been shown in previous figures, but are presented here to facilitate the discussion of the design. As the “I/Q” embodiment of the present invention is a subset of the PM embodiment, it will not be shown in a separate figure here, since the design approach will be very similar to that for the PM embodiment.
• Depending on the application and on the implementation, some of the design considerations may not apply. For example, and without limitation, in some cases it may not be necessary to optimize the pulse width or to include an amplifier.
• 7.1 Frequency of the Transmission Signal.
• The first step in the design process is to determine the frequency of the desiredtransmission signal5714. This is typically determined by the application for which the transmitter is to be used. The present invention is for a transmitter that can be used for all frequencies within the electromagnetic (EM) spectrum. For the examples herein, the explanation will focus on the use of the transmitter in the 900 MHz to 950 MHz range. Those skilled in the relevant art(s) will recognize that the analysis contained herein may be used for any frequency or frequency range.
• 7.2 Characteristics of the Transmission Signal.
• Once the frequency of the desiredtransmission signal5714 is known, the characteristics of the signal must be determined. These characteristics include, but are not limited to, whether the transmitter will operate at a fixed frequency or over a range of frequencies, and if it is to operate over a range of frequencies, whether those frequencies are continuous or are divided into discrete “channels.” If the frequency range is divided into discrete channels, the spacing between the channels must be ascertained. As an example, cordless phones operating in this frequency range may operate on discrete channels that are 50 KHz apart. That is, if the cordless phones operate in the 905 MHz to 915 MHz range (inclusive), the channels could be found at 905.000, 905.050, 905.100, . . . , 914.900, 914.950, and 915.000.
• 7.3 Modulation Scheme.
• Another characteristic that must be ascertained is the desired modulation scheme that is to be used. As described above in sections 2.1-2.2.4, above, these modulation schemes include FM, PM, AM, etc., and any combination or subset thereof, specifically including the widely used “I/Q” subset of PM. Just as the frequency of the desiredtransmission signal5714 is typically determined by the intended application, so too is the modulation scheme.
• 7.4 Characteristics of the Information Signal.
• The characteristics of aninformation signal5702 are also factors in the design of the transmitter circuit. Specifically, the bandwidth of theinformation signal5702 defines the minimum frequency for anoscillating signal5704,5738,5744 (for the FM, PM, and AM modes, respectively).
• 7.5 Characteristics of the Oscillating Signal.
• The desired frequency of theoscillating signal5704,5738,5744 is also a function of the frequency and characteristics of the desiredtransmission signal5714. Also, the frequency and characteristics of the desiredtransmission signal5714 are factors in determining the pulse width of the pulses in a string ofpulses5706. Note that the frequency of theoscillating signal5704,5738,5744 is substantially the same as the frequency of the string ofpulses5706. (An exception, which is discussed below, is when apulse shaping circuit5722 increases the frequency of theoscillating signal5704,5738,5744 in a manner similar to that described above in section 4.3.2.) Note also that the frequency and pulse width of the string ofpulses5706 is substantially the same as the frequency and pulse width of a harmonicallyrich signal5708.
• 7.5.1 Frequency of the Oscillating Signal.
• The frequency of theoscillating signal5704,5738,5744 must be a subharmonic of the frequency of the desiredtransmission signal5714. A subharmonic is the quotient obtained by dividing the fundamental frequency, in this case the frequency of the desiredtransmission signal5714, by an integer. When describing the frequency of certain signals, reference is often made herein to a specific value. It is understood by those skilled in the relevant art(s) that this reference is to the nominal center frequency of the signal, and that the actual signal may vary in frequency above and below this nominal center frequency based on the desired modulation technique being used in the circuit. As an example to be used herein, if the frequency of the desired transmission signal is 910 MHz, and it is to be used in an FM mode where, for example, the frequency range of the modulation is 40 KHz, the actual frequency of the signal will vary ±20 KHz around the nominal center frequency as a function of the information being transmitted. That is, the frequency of the desired transmission signal will actually range between 909.980 MHz and 910.020 MHz.
• The first ten subharmonics of a 910.000 MHz signal are given below.

  	harmonic	frequency
  	1st	910.000MHz
  	2nd	455.000
  	3rd	303.333 . . .
  	4th	227.500
  	5th	182.000
  	6th	151.666 . . .
  	7th	130.000
  	8th	113.750
  	9th	101.111 . . .
  	10th	91.000

  
  Theoscillating signal5704,5738,5744 can be at any one of these frequencies or, if desired, at a lower subharmonic. For discussion herein, the 9^thsubharmonic will be chosen. Those skilled in the relevant art(s) will understand that the analysis herein applies regardless of which harmonic is chosen. Thus the nominal center frequency of theoscillating signal5704,5738,5744 will be 101.1111 MHz. Recalling that in the FM mode, the frequency of the desiredtransmission signal5714 is actually 910.000 MHz±0.020 MHz, it can be shown that the frequency of theoscillating signal5704 will vary ±0.00222 MHz (i.e., from 101.10889 MHz to 101.11333 MHz). The frequency and frequency sensitivity of theoscillating signal5704 will drive the selection or design of the voltage controlled oscillator (VCO)5720.
• Another frequency consideration is the overall frequency range of the desired transmission signal. That is, if the transmitter is to be used in the cordless phone of the above example and will transmit on all channels between 905 MHz and 915 MHz, the VCO5720 (for the FM mode) or the local oscillator (LO)5734 (for the PM and AM modes) will be required to generateoscillating frequencies5704,5738,5744 that range from 100.5556 MHz to 101.6667 MHz. (That is, the 9^thsubharmonic of 910 MHz±5 MHz). In some applications, such as the cellular phone, the frequencies will change automatically, based on the protocols of the overall cellular system (e.g., moving from one cell to an adjacent cell). In other applications, such as a police radio, the frequencies will change based on the user changing channels.
• In some applications, different models of the same transmitter will transmit signals at different frequencies, but each model will, itself, only transmit a single frequency. A possible example of this might be remote controlled toy cars, where each toy car operates on its own frequency, but, in order for several toy cars to operate in the same area, there are several frequencies at which they could operate. Thus, the design of theVCO5720 orLO5734 will be such that it is able to be tuned to a set frequency when the circuit is fabricated, but the user will typically not be able to adjust the frequency.
• It is well known to those skilled in the relevant art(s) that several of the criteria to be considered in the selection or design of an oscillator (VCO5720 or LO5734) include, but are not limited to, the nominal center frequency of the desiredtransmission signal5714, the frequency sensitivity caused by the desired modulation scheme, the range of all possible frequencies for the desiredtransmission signal5714, and the tuning requirements for each specific application. Another important criterion is the determination of the subharmonic to be used, but unlike the criteria listed above which are dependent on the desired application, there is some flexibility in the selection of the subharmonic.
• 7.5.2 Pulse Width of the String of Pulses.
• Once the frequency of theoscillating signal5704,5738,5744 has been selected, the pulse width of the pulses in the stream ofpulses5706 must be determined. (See sections 4-4.3.4, above, for a discussion of harmonic enhancement and the impact the pulse-width-to-period ratio has on the relative amplitudes of the harmonics in a harmonicallyrich signal5708.) In the example used above, the 9^thsubharmonic was selected as the frequency of theoscillating signal5704,5738,5744. In other words, the frequency of the desired transmission signal will be the 9^thharmonic of theoscillating signal5704,5738,5744. One approach in selecting the pulse width might be to focus entirely on the frequency of theoscillating signal5704,5738,5744 and select a pulse width and observe its operation in the circuit. For the case where the harmonicallyrich signal5708 has a unity amplitude, and the pulse-width-to-period ratio is 0.1, the amplitude of the 9^thharmonic will be 0.0219. Looking again at Table6000 andFIG. 58 it can be seen that the amplitude of the 9^thharmonic is higher than that of the 10^thharmonic (which is zero) but is less than half the amplitude of the 8^thharmonic. Because the 9^thharmonic does have an amplitude, this pulse-width-to-period ratio could be used with proper filtering. Typically, a different ratio might be selected to try and find a ratio that would provide a higher amplitude.
• Looking at Eq. 1 in section 4.1.1, it is seen that the relative amplitude of any harmonic is a function of the number of the harmonic and the pulse-width-to-period ratio of the underlying waveform. Applying calculus of variations to the equation, the pulse-width-to-period ratio that yields the highest amplitude harmonic for any given harmonic can be determined.
• From Eq. 1, where A_nis the amplitude of the n^thharmonic,
  A_n=[A_pulse][(2/π)/n]sin{n·π·(τ/T)]  Eq. 2
  If the amplitude of the pulse, A_pulse, is set to unity (i.e., equal to 1), the equation becomes
  A_n=[2/(n·π)]sin[n·π·(τ/T)]  Eq. 3
  From this equation, it can be seen that for any value of n (the harmonic) the amplitude of that harmonic, A_n, is a function of the pulse-width-to-period ratio, τ/T. To determine the highest value of A_nfor a given value of n, the first derivative of A_nwith respect to τ/T is taken. This gives the following equations.$\begin{array}{cc}\delta \left(A_n\right)/\delta \left(\tau /T\right)=\delta \left\{\left[2/\left(n·\pi \right)\right]\sin \left[n·\pi ·\left(\tau /T\right)\right]\right\}/\delta \left(\tau /T\right)& \mathrm{Eq}.4\\ =\left[2/\left(n·\pi \right)\right]\delta [\sin \left[n·\pi \left(\tau /T\right)\right]/\delta \left(\tau /T\right)& \mathrm{Eq}.5\\ =\left[2/\left(n·\pi \right)\right]\cos \left[n·\pi ·\left(\tau /T\right)\right]& \mathrm{Eq}.6\end{array}$
• From calculus of variations, it is known that when the first derivative is set equal to zero, the value of the variable that will yield a relative maximum (or minimum) can be determined.
  δ(A_n)/δ(τ/T)=0  Eq. 7
  [2/(n·π)]cos[n·π·(τ/T)]=0  Eq. 8
  cos[n·π·(τ/T)]=0  Eq. 9
  From trigonometry, it is known that for Eq. 9 to be true,
  n·π·(τ/T)=π/2 (or 3π/2, 5π/2, etc.)  Eq. 10
  τ/T=(π/2)/(n·π)
  τ/T=1/(2·n) (or 3/(2·n), 5/(2·n), etc.)  Eq. 12
  The above derivation is well known to those skilled in the relevant art(s). From Eq. 12, it can be seen that if the pulse-width-to-period ratio is equal to 1/(2·n), the amplitude of the harmonic should be substantially optimum. For the case of the 9^thharmonic, Eq. 12 will yield a pulse-width-to-period ratio of 1/(2·9) or 0.0556. For the amplitude of this 9^thharmonic, Table6100 ofFIG. 61 shows that it is 0.0796. This is an improvement over the previous amplitude for a pulse-width-to-period ratio of 0.1. Table6100 also shows that the 9^thharmonic for this pulse-width-to-period ratio has the highest amplitude of any 9^thharmonic, which bears out the derivation above. The frequency spectrum for a pulse-width-to-period ratio of 0.0556 is shown inFIG. 59. (Note that other pulse-width-to-period ratios of 3/(2·n), 5/(2·n), etc., will have amplitudes that are equal to but not larger than this one.)
• This is one approach to determining the desired pulse-width-to-period ratio. Those skilled in the relevant art(s) will understand that other techniques may also be used to select a pulse-width-to-period ratio.
• 7.6 Design of the Pulse Shaping Circuit.
• Once the determination has been made as to the desired frequency of theoscillating signal5704,5738,5744 and of the pulse width, thepulse shaping circuit5722 can be designed. Looking back to sections 4-4.3.4 it can be seen that thepulse shaping circuit5722 can not only produce a pulse of a desired pulse width, but it can also cause the frequency of the string ofpulses5706 to be higher than the frequency of theoscillating signal5704,5738,5744. Recall that the pulse-width-to-period ratio applies to the pulse-width-to-period ratio of the harmonicallyrich signal5708 and not to the pulse-width-to-period ratio of theoscillating signal5704,5738,5744, and that the frequency and pulse width of the harmonicallyrich signal5708 mirrors the frequency and pulse width of the string ofpulses5706. Thus, if in the selection of theVCO5720 orLO5734 it was desired to choose an oscillator that is lower than that required for the selected harmonic, the pulse shaping circuit5733 can be used to increase the frequency. Going back to the previous example, the frequency of theoscillating signal5704,5738,5744 could be 50.5556 MHz rather than 101.1111 MHz if thepulse shaping circuit5722 was designed such as discussed in sections 4.2.24.2.2.2 (shown inFIGS. 40A-40D) not only to shape the pulse, but also to double the frequency. While that discussion was specifically for a square wave input, those skilled in the relevant art(s) will understand that similar techniques will apply to non-rectangular waveforms (e.g., a sinusoidal wave). This use of the pulse shaping circuit to double the frequency has a possible advantage in that it allows the design and selection of an oscillator (VCO5720 of LO5734) with a lower frequency, if that is a consideration.
• It should also be understood that thepulse shaping circuit5722 is not always required. If the design or selection of theVCO5720 orLO5734 was such that theoscillating signal5704,5738,5744 was a substantially rectangular wave, and that substantially rectangular wave had a pulse-width-to-period ratio that was adequate, thepulse shaping circuit5722 could be eliminated.
• 7.7 Selection of the Switch.
• The selection of aswitch5724 can now be made. Theswitch5724 is shown in the examples ofFIGS. 57A, 57B, and57C as a GaAsFET. However, it may be any switching device of any technology that can open and close “crisply” enough to accommodate the frequency and pulse width of the string ofpulses5706.
• 7.7.1 Optimized Switch Structures.
• Switches of Different Sizes
• In an embodiment, the switch modules discussed herein can be implemented as a series of switches operating in parallel as a single switch. The series of switches can be transistors, such as, for example, field effect transistors (FET), bi-polar transistors, or any other suitable circuit switching devices. The series of switches can be comprised of one type of switching device, or a combination of different switching devices.
• For example,FIG. 73 illustrates aswitch module7300. InFIG. 73, the switch module is illustrated as a series of FETs7302a-n. The FETs7302a-ncan be any type of FET, including, but not limited to, a MOSFET, a JFET, a GaAsFET, etc. Each of FETs7302a-nincludes a gate7304a-n, a source7306a-n, and a drain7308a-n. The series of FETs7302a-noperate in parallel. Gates7304a-nare coupled together, sources7306a-nare coupled together, and drains7308a-nare coupled together. Each of gates7304a-nreceives thecontrol signal2804,3104 to control the switching action between corresponding sources7306a-nand drains7308a-n. Generally, the corresponding sources7306a-nand drains7308a-nof each of FETs7302a-nare interchangeable. There is no numerical limit to the number of FETs. Any limitation would depend on the particular application, and the “a-n” designation is not meant to suggest a limit in any way.
• In an embodiment, FETs7302a-nhave similar characteristics. In another embodiment, one or more of FETs7302a-nhave different characteristics than the other FETs. For example, FETs7302a-nmay be of different sizes. In CMOS, generally, the larger size a switch is (meaning the larger the area under the gate between the source and drain regions), the longer it takes for the switch to turn on. The longer turn on time is due in part to a higher gate to channel capacitance that exists in larger switches. Smaller CMOS switches turn on in less time, but have a higher channel resistance. Larger CMOS switches have lower channel resistance relative to smaller CMOS switches. Different turn on characteristics for different size switches provides flexibility in designing an overall switch module structure. By combining smaller switches with larger switches, the channel conductance of the overall switch structure can be tailored to satisfy given requirements.
• In an embodiment, FETs7302a-nare CMOS switches of different relative sizes. For example,FET7302amay be a switch with a smaller size relative to FETs7302b-n.FET7302bmay be a switch with a larger size relative toFET7302a, but smaller size relative to FETs7302c-n. The sizes ofFETs7302c-nalso may be varied relative to each other. For instance, progressively larger switch sizes may be used. By varying the sizes of FETs7302a-nrelative to each other, the turn on characteristic curve of the switch module can be correspondingly varied. For instance, the turn on characteristic of the switch module can be tailored such that it more closely approaches that of an ideal switch. Alternately, the switch module could be tailored to produce a shaped conductive curve.
• By configuring FETs7302a-nsuch that one or more of them are of a relatively smaller size, their faster turn on characteristic can improve the overall switch module turn on characteristic curve. Because smaller switches have a lower gate to channel capacitance, they can turn on more rapidly than larger switches.
• By configuring FETs7302a-nsuch that one or more of them are of a relatively larger size, their lower channel resistance also can improve the overall switch module turn on characteristics. Because larger switches have a lower channel resistance, they can provide the overall switch structure with a lower channel resistance, even when combined with smaller switches. This improves the overall switch structure's ability to drive a wider range of loads. Accordingly, the ability to tailor switch sizes relative to each other in the overall switch structure allows for overall switch structure operation to more nearly approach ideal, or to achieve application specific requirements, or to balance trade-offs to achieve specific goals, as will be understood by persons skilled in the relevant arts(s) from the teachings herein.
• It should be understood that the illustration of the switch module as a series of FETs7302a-ninFIG. 73 is for example purposes only. Any device having switching capabilities could be used to implement the switch module, as will be apparent to persons skilled in the relevant art(s) based on the discussion contained herein.
• Reducing Overall Switch Area
• Circuit performance also can be improved by reducing overall switch area. As discussed above, smaller switches (i.e., smaller area under the gate between the source and drain regions) have a lower gate to channel capacitance relative to larger switches. The lower gate to channel capacitance allows for lower circuit sensitivity to noise spikes.FIG. 74A illustrates an embodiment of a switch module, with a large overall switch area. The switch module ofFIG. 74A includes twenty FETs7402-7440. As shown, FETs7402-7440 are the same size (“Wd” and “lng” parameters are equal). Input source7446 produces the input EM signal.Pulse generator7448 produces the energy transfer signal for FETs7402-7440. Capacitor Cl is the storage element for the input signal being sampled by FETs7402-7440.FIGS. 74B-74Q illustrate example waveforms related to the switch module ofFIG. 74A.FIG. 74B shows a received 1.01 GHz EM signal to be sampled and downconverted to a 10 MHZ intermediate frequency signal.FIG. 74C shows an energy transfer signal having an aliasing rate of 200 MHZ, which is applied to the gate of each of the twenty FETs7402-7440. The energy transfer signal includes a train of energy transfer pulses having non-negligible apertures that tend away from zero time in duration. The energy transfer pulses repeat at the aliasing rate.FIG. 74D illustrates the affected received EM signal, showing effects of transferring energy at the aliasing rate, atpoint7442 ofFIG. 74A.FIG. 74E illustrates a down-converted signal atpoint7444 ofFIG. 74A, which is generated by the down-conversion process.
• FIG. 74F illustrates the frequency spectrum of the received 1.01 GHz EM signal.FIG. 74G illustrates the frequency spectrum of the received energy transfer signal.FIG. 74H illustrates the frequency spectrum of the affected received EM signal atpoint7442 ofFIG. 74A.FIG. 741 illustrates the frequency spectrum of the down-converted signal atpoint7444 ofFIG. 74A.
• FIGS. 74J-74M respectively further illustrate the frequency spectrums of the received 1.01 GHz EM signal, the received energy transfer signal, the affected received EM signal atpoint7442 ofFIG. 74A, and the down-converted signal atpoint7444 ofFIG. 74A, focusing on a narrower frequency range centered on 1.00 GHz. As shown inFIG. 74L, a noise spike exists at approximately 1.0 GHz on the affected received EM signal atpoint7442 ofFIG. 74A. This noise spike may be radiated by the circuit, causing interference at 1.0 GHz to nearby receivers.
• FIGS. 74N-74Q respectively illustrate the frequency spectrums of the received 1.01 GHz EM signal, the received energy transfer signal, the affected received EM signal atpoint7442 ofFIG. 74A, and the down-converted signal atpoint7444 ofFIG. 74A, focusing on a narrow frequency range centered near 10.0 MHZ. In particular,FIG. 74Q shows that an approximately 5 mV signal was downconverted at approximately 10 MHZ.
• FIG. 75A illustrates an alternative embodiment of the switch module, this time with fourteen FETs7502-7528 shown, rather than twenty FETs7402-7440 as shown inFIG. 74A. Additionally, the FETs are of various sizes (some “Wd” and “1 ng” parameters are different between FETs).
• FIGS. 75B-75Q, which are example waveforms related to the switch module ofFIG. 75A, correspond to the similarly designated figures ofFIGS. 74B-74Q. AsFIG. 75L shows, a lower level noise spike exists at 1.0 GHz than at the same frequency ofFIG. 74L. This correlates to lower levels of circuit radiation. Additionally, asFIG. 75Q shows, the lower level noise spike at 1.0 GHz was achieved with no loss in conversion efficiency. This is represented inFIG. 75Q by the approximately 5 mV signal downconverted at approximately 10 MHZ. This voltage is substantially equal to the level downconverted by the circuit ofFIG. 74A. In effect, by decreasing the number of switches, which decreases overall switch area, and by reducing switch area on a switch-by-switch basis, circuit parasitic capacitance can be reduced, as would be understood by persons skilled in the relevant art(s) from the teachings herein. In particular this may reduce overall gate to channel capacitance, leading to lower amplitude noise spikes and reduced unwanted circuit radiation.
• It should be understood that the illustration of the switches above as FETs inFIGS. 74A-74Q and75A-75Q is for example purposes only. Any device having switching capabilities could be used to implement the switch module, as will be apparent to persons skilled in the relevant art(s) based on the discussion contained herein.
• Charge Injection Cancellation
• In embodiments wherein the switch modules discussed herein are comprised of a series of switches in parallel, in some instances it may be desirable to minimize the effects of charge injection. Minimizing charge injection is generally desirable in order to reduce the unwanted circuit radiation resulting therefrom. In an embodiment, unwanted charge injection effects can be reduced through the use of complementary n-channel MOSFETs and p-channel MOSFETs. N-channel MOSFETs and p-channel MOSFETs both suffer from charge injection. However, because signals of opposite polarity are applied to their respective gates to turn the switches on and off, the resulting charge injection is of opposite polarity. Resultingly, n-channel MOSFETs and p-channel MOSFETs may be paired to cancel their corresponding charge injection. Hence, in an embodiment, the switch module may be comprised of n-channel MOSFETs and p-channel MOSFETS, wherein the members of each are sized to minimize the undesired effects of charge injection.
• FIG. 77A illustrates an alternative embodiment of the switch module, this time with fourteen n-channel FETs7702-7728 and twelve p-channel FETs7730-7752 shown, rather than twenty FETs7402-7440 as shown inFIG. 74A. The n-channel and p-channel FETs are arranged in a complementary configuration. Additionally, the FETs are of various sizes (some “Wd” and “1 ng” parameters are different between FETs).
• FIGS. 77B-77Q, which are example waveforms related to the switch module ofFIG. 77A, correspond to the similarly designated figures ofFIGS. 74B-74Q. AsFIG. 77L shows, a lower level noise spike exists at 1.0 GHz than at the same frequency ofFIG. 74L. This correlates to lower levels of circuit radiation. Additionally, asFIG. 77Q shows, the lower level noise spike at 1.0 GHz was achieved with no loss in conversion efficiency. This is represented inFIG. 77Q by the approximately 5 mV signal downconverted at approximately 10 MHZ. This voltage is substantially equal to the level downconverted by the circuit ofFIG. 74A. In effect, by arranging the switches in a complementary configuration, which assists in reducing charge injection, and by tailoring switch area on a switch-by-switch basis, the effects of charge injection can be reduced, as would be understood by persons skilled in the relevant art(s) from the teachings herein. In particular this leads to lower amplitude noise spikes and reduced unwanted circuit radiation.
• It should be understood that the use of FETs inFIGS. 77A-77Q in the above description is for example purposes only. From the teachings herein, it would be apparent to persons of skill in the relevant art(s) to manage charge injection in various transistor technologies using transistor pairs.
• Overlapped Capacitance
• The processes involved in fabricating semiconductor circuits, such as MOSFETs, have limitations. In some instances, these process limitations may lead to circuits that do not function as ideally as desired. For instance, a non-ideally fabricated MOSFET may suffer from parasitic capacitances, which in some cases may cause the surrounding circuit to radiate noise. By fabricating circuits with structure layouts as close to ideal as possible, problems of non-ideal circuit operation can be minimized.
• FIG. 76A illustrates a cross-section of an example n-channel enhancement-mode MOSFET7600, with ideally shaped n+regions.MOSFET7600 includes agate7602, achannel region7604, asource contact7606, asource region7608, adrain contact7610, adrain region7612, and aninsulator7614.Source region7608 and drainregion7612 are separated by p-type material ofchannel region7604.Source region7608 and drainregion7612 are shown to be n+material. The n+material is typically implanted in the p-type material ofchannel region7604 by an ion implantation/diffusion process. Ion implantation/diffusion processes are well known by persons skilled in the relevant art(s).Insulator7614 insulatesgate7602 which bridges over the p-type material.Insulator7614 generally comprises a metal-oxide insulator. The channel current betweensource region7608 and drainregion7612 forMOSFET7600 is controlled by a voltage atgate7602.
• Operation ofMOSFET7600 shall now be described. When a positive voltage is applied togate7602, electrons in the p-type material ofchannel region7604 are attracted to the surface belowinsulator7614, forming a connecting near-surface region of n-type material between the source and the drain, called a channel. The larger or more positive the voltage between thegate contact7606 andsource region7608, the lower the resistance across the region between.
• InFIG. 76A,source region7608 and drainregion7612 are illustrated as having n+regions that were formed into idealized rectangular regions by the ion implantation process.FIG. 76B illustrates a cross-section of an example n-channel enhancement-mode MOSFET7616 with non-ideally shaped n+regions.Source region7620 and drainregion7622 are illustrated as being formed into irregularly shaped regions by the ion implantation process. Due to uncertainties in the ion implantation/diffusion process, in practical applications,source region7620 and drainregion7622 do not form rectangular regions as shown in FIG.76A.FIG. 76B showssource region7620 and drainregion7622 forming exemplary irregular regions. Due to these process uncertainties, the n+regions ofsource region7620 and drainregion7622 also may diffuse further than desired into the p-type region ofchannel region7618, extending underneathgate7602 The extension of thesource region7620 and drainregion7622 underneathgate7602 is shown as source overlap7624 anddrain overlap7626.Source overlap7624 anddrain overlap7626 are further illustrated inFIG. 76C.FIG. 76C illustrates a top-level view of an example layout configuration forMOSFET7616.Source overlap7624 anddrain overlap7626 may lead to unwanted parasitic capacitances betweensource region7620 andgate7602, and betweendrain region7622 andgate7602. These unwanted parasitic capacitances may interfere with circuit function. For instance, the resulting parasitic capacitances may produce noise spikes that are radiated by the circuit, causing unwanted electromagnetic interference.
• As shown inFIG. 76C, anexample MOSFET7616 may include agate pad7628.Gate7602 may include agate extension7630, and agate pad extension7632.Gate extension7630 is an unused portion ofgate7602 required due to metal implantation process tolerance limitations.Gate pad extension7632 is a portion ofgate7602 used to couplegate7602 togate pad7628. The contact required forgate pad7628 requiresgate pad extension7632 to be of non-zero length to separate the resulting contact from the area betweensource region7620 and drainregion7622. This preventsgate7602 from shorting to the channel betweensource region7620 and drain region7622 (insulator7614 ofFIG. 76B is very thin in this region). Unwanted parasitic capacitances may form betweengate extension7630 and the substrate (FET7616 is fabricated on a substrate), and betweengate pad extension7632 and the substrate. By reducing the respective areas ofgate extension7630 andgate pad extension7632, the parasitic capacitances resulting therefrom can be reduced. Accordingly, embodiments address the issues of uncertainty in the ion implantation/diffusion process. it will be obvious to persons skilled in the relevant art(s) how to decrease the areas ofgate extension7630 andgate pad extension7632 in order to reduce the resulting parasitic capacitances.
• It should be understood that the illustration of the n-channel enhancement-mode MOSFET is for example purposes only. The present invention is applicable to depletion mode MOSFETs, and other transistor types, as will be apparent to persons skilled in the relevant art(s) based on the discussion contained herein.
• 7.7.2 Phased D2D—Splitter in CMOS.
• FIG. 72A illustrates an embodiment of asplitter circuit7200 implemented in CMOS. This embodiment is provided for illustrative purposes, and is not limiting. In an embodiment,splitter circuit7200 is used to split a local oscillator (LO) signal into two oscillating signals that are approximately 90° out of phase. The first oscillating signal is called the I-channel oscillating signal. The second oscillating signal is called the Q-channel oscillating signal. The Q-channel oscillating signal lags the phase of the I-channel oscillating signal by approximately 90°.Splitter circuit7200 includes a first I-channel inverter7202, a second I-channel inverter7204, a third I-channel inverter7206, a first Q-channel inverter7208, a second Q-channel inverter7210, an I-channel flip-flop7212, and a Q-channel flip-flop7214.
• FIGS.72F-J are example waveforms used to illustrate signal relationships ofsplitter circuit7200. The waveforms shown in FIGS.72F-J reflect ideal delay times throughsplitter circuit7200 components.LO signal7216 is shown inFIG. 72F. First, second, and third I-channel inverters7202,7204, and7206invert LO signal7216 three times, outputtinginverted LO signal7218, as shown inFIG. 72G. First and second Q-channel inverters7208 and7210invert LO signal7216 twice, outputtingnon-inverted LO signal7220, as shown inFIG. 72H. The delay through first, second, and third I-channel inverters7202,7204, and7206 is substantially equal to that through first and second Q-channel inverters7208 and7210, so thatinverted LO signal7218 andnon-inverted LO signal7220 are approximately 180° out of phase. The operating characteristics of the inverters may be tailored to achieve the proper delay amounts, as would be understood by persons skilled in the relevant art(s).
• I-channel flip-flop7212 inputs invertedLO signal7218. Q-channel flip-flop7214 inputs non-invertedLO signal7220. In the current embodiment, I-channel flip-flop7212 and Q-channel flip-flop7214 are edge-triggered flip-flops. When either flip-flop receives a rising edge on its input, the flip-flop output changes state. Hence, 1-channel flip-flop7212 and Q-channel flip-flop7214 each output signals that are approximately half of the input signal frequency. Additionally, as would be recognized by persons skilled in the relevant art(s), because the inputs to I-channel flip-flop7212 and Q-channel flip-flop7214 are approximately 180° out of phase, their resulting outputs are signals that are approximately 90° out of phase. I-channel flip-flop7212 outputs I-channel oscillating signal7222, as shown inFIG. 721. Q-channel flip-flop7214 outputs Q-channel oscillating signal7224, as shown inFIG. 72J. Q-channel oscillating signal7224 lags the phase of 1-channel oscillating signal7222 by 90°, also as shown in a comparison ofFIGS. 72I and 72J.
• FIG. 72B illustrates a more detailed circuit embodiment of thesplitter circuit7200 ofFIG. 72. The circuit blocks ofFIG. 72B that are similar to those ofFIG. 72A are indicated by corresponding reference numbers. FIGS.72C-D show example output waveforms relating to thesplitter circuit7200 ofFIG. 72B.FIG. 72C shows I-channel oscillating signal7222.FIG. 72D shows Q-channel oscillating signal7224. As is indicated by a comparison ofFIGS. 72C and 72D, the waveform of Q-channel oscillating signal7224 ofFIG. 72D lags the waveform of 1-channel oscillating signal7222 ofFIG. 72C by approximately 90°.
• It should be understood that the illustration of thesplitter circuit7200 inFIGS. 72A and 72B is for example purposes only.Splitter circuit7200 may be comprised of an assortment of logic and semiconductor devices of a variety of types, as will be apparent to persons skilled in the relevant art(s) based on the discussion contained herein.
• 7.8 Design of the Filter.
• The design of thefilter5726 is determined by the frequency and frequency range of the desiredtransmission signal5714. As discussed above in sections 3.3.9-3.3.9.2, the term. “Q” is used to describe the ratio of the center frequency of the output of the filter to the bandwidth of the “3 dB down” point. The trade offs that were made in the selection of the subharmonic to be used is a factor in designing the filter. That is, if, as an excursion to the example given above, the frequency of the desired transmission signal were again 910 MHz, but the desired subharmonic were the 50′ subharmonic, then the frequency of that 50^thsubharmonic would be 18.2000 MHz. This means that the frequencies seen by the filter will be 18.200 MHz apart. Thus, the “Q” will need to be high enough to avoid allowing information from the adjacent frequencies being passed through. The other consideration for the “Q” of the filter is that it must not be so tight that it does not permit the usage of the entire range of desired frequencies.
• 7.9 Selection of an Amplifier.
• Anamplifier module5728 will be needed if the signal is not large enough to be transmitted or if it is needed for some downstream application. This can occur because the amplitude of the resultant harmonic is too small. It may also occur if thefilter5726 has attenuated the signal.
• 7.10 Design of the Transmission Module.
• Atransmission module5730, which is optional, ensures that the output of thefilter5726 and theamplifier module5728 is able to be transmitted. In the implementation wherein the transmitter is used to broadcast EM signals over the air, the transmission module matches the impedance of the output of theamplifier module5728 and the input of anantenna5732. This techniques is well known to those skilled in the relevant art(s). If the signal is to be transmitted over a point-to-point line such as a telephone line (or a fiber optic cable) thetransmission module5730 may be a line driver (or an electrical-to-optical converter for fiber optic implementation).

Claims (1)

1. A system for up-converting an electromagnetic signal, the electromagnetic signal having a first frequency, comprising:

means for gating a bias signal at a rate proportional to the first frequency of the electromagnetic signal to generate a harmonically rich signal having a plurality of harmonics, said gating means including an optimized switch structure; and

means for selecting at least one of said plurality of harmonics as a desired signal having at least a second frequency.

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