CN1130823A - Satellite receiving tuner with band broadness changeable demodulation circuit - Google Patents

Abstract

A satellite receiving tuner with functions of dual inputs, variable bandwidth and demodulation features that the RF signals (950-2050 MHZ) received from satellite pass through low-pass filter, RF amplifier, tracking filter, attenuator circuit and microwave amplifier and frequency converter IC to form MF signals, which further pass through 2-stage MF amplifier, comb filter and bandwidth-variable demodulator to output base-frequency signals. Its bandwidth may be changed according to size of outdoor antenna to obtain optimal receiving and threshold properties.

Description

Satellite receiver turning with band broadness changeable demodulation circuit

The present invention relates to a kind of satellite receiving circuit, relate to a kind of satellite receiver turning or rather.

Direct broadcasting satellite DBS (Direct Broadcasting Satellite) is in transmission course, the ground transmitting station is with fundamental frequency signals such as sound and images, after multiplex circuit (multiplexer) is done the reasonable time distribution, be tuned as intermediate-freuqncy signal, this signal is via radio-frequency modulator and power amplifier, change radiofrequency signal RF (Radio Frequency) into, again this radiofrequency signal antennas heavenwards width of cloth is penetrated.The ground receiving platform need have low noise, wide band RF receiving ability, could amplify the RF signal that is received, and amplified signal is converted to lower intermediate-freuqncy signal, and then this intermediate-freuqncy signal is taken out wherein fundamental frequency signal via demodulator circuit, comprise video and voice signal.

Terrestrial receiving antenna very easily is subjected to the interference or the intrusion of other signals, and influences the reliability of communication system when receiving from atmospheric electromagnetic wave signal.In addition, traditional broadband direct broadcasting satellite receiver turning with demodulation function, need with the frequency range range fit that sets, and select the reception antenna of suitable specification for use, could receive in the more weak area of signal, in case the antenna size specification changes, broken away from the frequency range scope that receiver turning sets, then very easily be subjected to the interference or the intrusion of other signals, the antenna receptivity reduced, and influence television picture quality.

The objective of the invention is to design a kind of satellite receiver turning with band broadness changeable demodulation circuit, make via the frequency range after the demodulator circuit demodulation, can cooperate the change of antenna size, and the acquisition good reception characteristics, electrical characteristics such as noise-reduction coefficient, raising output gain and thresholding, by this design, can reduce the size of antenna simultaneously, reduce the shared space of satellite antenna with satellite receiver turning of band broadness changeable demodulation circuit.

Satellite receiver turning with band broadness changeable demodulation circuit of the present invention, it is a kind of broadband direct broadcasting satellite tuner with dual input variable ratio frequency changer demodulation function, in the band broadness changeable demodulation device, establish a variable ratio frequency changer stretch circuit, this variable ratio frequency changer stretch circuit is controlled by demodulating voltage, change the electric current that flows through diode, make the frequency range after the demodulation adapt to the change of antenna size, and improve the electrical characteristic of tuner.

Further specify technology of the present utility model below in conjunction with embodiment and accompanying drawing

Fig. 1 is the satellite receiver turning theory diagram with band broadness changeable demodulation circuit

Fig. 2 is the circuit theory diagrams of radio frequency input circuit among Fig. 1

Fig. 3 is that frequency conversion among Fig. 1, intermediate frequency amplify and the band broadness changeable demodulation circuit schematic diagram

Referring to Fig. 1, have the satellite receiver turning of band broadness changeable demodulation circuit, mainly comprise radiofrequency input circuit 1, amplify frequency changer circuit 2, intermediatefrequency amplifier circuit 3 and band broadnesschangeable demodulation circuit 4.

Referring to Fig. 2, and in conjunction with referring to Fig. 1, radiofrequency input circuit 1 by low pass filter 11,11 ',radio frequency amplifier 12,12 ' and switching circuit 13 constitute.Radio frequency amplifier 12,12 ' output are connected with 13 liang of inputs of switching circuit respectively, and the output of switching circuit 13 then connects the input that amplifies frequency changer circuit 2.

Low pass filter 11,11 ' is used to receive the radiofrequency signal of satellite antenna, and switching circuit 13 is by A/B input selector switch SW1, transistor Q2, Q3, diode D3, D4 resistance R 40, R44, R53, R55, R45, and elements such as capacitor C 70, C71 connect and compose.Be subjected to the control of switching circuit 13, make the radiofrequency signal after the reception can be delivered to the input A of low pass filter 11 or the input B of another low pass filter 11 '.Promptly when the A/B of switching circuit 13 input selector switch SW1 is high potential, transistor Q2 and diode D4 (joining with the Q end among Fig. 3) keep conducting state, transistor Q3 and diode D3 (joining with the P end among Fig. 3) then remain on nonconducting state, this moment is by capacitor C 60, C61, C62, C63, C64, C65,inductance L 1 and microstrip circuit SL3, the low pass filter 11 that SL5 formed will receive the radiofrequency signal (950-2050MHZ) (being connected with LNBA among Fig. 3 by N end) of satellite antenna and with the target signal filter of 2050MHZ with upper frequency, and make its impedance matching, and then the signal of this low pass filter 11 outputs delivered to by coupling capacitance C66, transistor Q1, diode D1, bias resistance 49, R 50, R51, ground capacity C67 and R52, theradio frequency amplifier 12 that elements such as C69 microstrip circuit SL7 are formed amplifies.

The signal thatradio frequency amplifier 12 is exported after with low pass filter 11 filtering amplifies, and delivers to amplification frequency changer circuit 2 through capacitor C 70 with diode D4 (linking to each other through Q and Fig. 3 end of the same name).Decoupling circuit R52, C69 are used to stop high-frequency signal to enter diode D4 by R53.

In like manner, when the A/B of switching circuit 13 input selector switch SW1 is electronegative potential, transistor Q3, diode D3 keeps conducting state, this moment is by capacitor C 43, C45, C46, C47, C48, C49, inductance L 2 and microstrip circuit SL4, the low pass filter 11 ' that SL6 formed receives the radiofrequency signal (being connected with LNBB among Fig. 3 by the M end) of satellite antenna, and filtering is higher than the above signal of 2050MHZ frequency, and make its impedance matching, and then the signal of low pass filter 11 ' output delivered to by coupling capacitance C52, transistor Q4, diode D2, bias resistance R39, R41, R43, ground capacity C53,resistance R 42, the radio frequency amplifier 12 ' that capacitor C 54 and microstrip circuit SL8 are formed amplifies.Amplifying signal is delivered to through capacitor C 71, diode D3 (being connected through P and Fig. 3 end of the same name) and is amplified frequency changer circuit 2, and decoupling circuit R42, C54 are used to stop high-frequency signal to enter diode D3 by resistance R 44 in the radio frequency amplifier 12 '.

Referring to Fig. 3, and combination is referring to Fig. 1, amplifying frequency changer circuit 2 is made up of the integrated amplificationfrequency changer circuit 23 of tracking filter 21, attenuator circuit 22 and microwave monolithic, wherein tracking filter 21 inputs are connected with the output of radiofrequency input circuit 1, tracking filter 21 outputs connect the input of attenuator circuit 22, the output of attenuator circuit 22 connects the input of microwave monolithicintegrated circuit 23, and the output of microwave monolithicintegrated circuit 23 then is connected with intermediate frequency amplifier circuit 3.In addition, attenuator circuit 22 also is connected with automatic gain control circuit AGC (Automatic Gain Control).

Tracking filter 21 is byinductance L 3, resistance R 70, R24, capacitor C 13, C14, C15, C73, C12, variable capacitance diode D8, D9 and microstripline SL9, SL10, SL11, elements such as SL12 are formed, the output signal of receivedRF input circuit 1, and to this output signal filtering, the filtering picture frequency, to deliver to by coupling capacitance C17 through filtered signal again, diode D10,resistance R 27, R28, capacitor C 19, C32, C22 and match circuit C20, C21, the attenuator circuit 22 that SL13 formed, wherein match circuit C20, C21, SL13 is used to suppress the low frequency signal gain.

Attenuator circuit 22 is decayed the output signal of the tracking filter 21 of reception, noise when improving strong signal disturbs, and be subjected to the control of automatic gain control circuit AGC, the gain of control decay back signal, and then the signal after will decaying delivers to the microwave monolithic integrated circuit MMIC (Microwave Monlithicinlergarated Circuit) 23 that is made up of integrated circuit (IC) 1, resistance R 58, R59, elements such as variable capacitance diode D6, D7, amplifies frequency conversion.

The output signal of the integrated amplificationfrequency changer circuit 23 receiving attenuation circuit 22 of this microwave monolithic, and this signal sent into its inner radio frequency amplifier and voltage-controlled oscillator, produce intermediate-freuqncy signal in the superhet mode, send intermediatefrequency amplifier circuit 3 to be amplified through its output this intermediate-freuqncy signal again.

Intermediatefrequency amplifier circuit 3 is made up of first orderintermediate frequency amplifier 31,comb filter 32 and 33,34 of second level intermediate frequency amplifiers, the input of first orderintermediate frequency amplifier 31 is connected with the output that amplifies frequency changer circuit 2, the output of puttingdevice 31 in the first order connectscomb filter 32,comb filter 32 outputs connect the input ofputting device 33,34 in the second level respectively, the output of puttingdevice 33,34 in the second level then is connected with the input of band broadnesschangeable demodulation circuit 4, in addition, puttingdevice 31 in the first order also is connected with automatic gain control circuit AGC.

Putdevice 31 in the first order by double-gate field-effect transistor Q6, bias resistance R32, R33, R34, R35, R36, R69, ground capacity C25, C39 reach the match circuit of being made up ofinductance L 4, resistance R 37, capacitor C 35, C36, C41, C24 and are formed, be used to receive the intermediate-freuqncy signal of amplifying frequency changer circuit 2 outputs, and amplify this signal, under the control of automatic gain control circuit AGC, control the gain or the decay of this intermediate-freuqncy signal, sendcomb filter 32 with signal through its output then.

Comb filter 32 will through in put the intermediate-freuqncy signal thatdevice 31 amplifies, select the intermediate-freuqncy signal of frequency range 16MH2 and 27MHZ to amplify, and the signal after will amplifying is delivered to the intermediate frequency amplifier of being made up of elements such as integrated circuit (IC) 3, ground capacity C105, coupling capacitance C104,C108 33 respectively, or, amplified by the intermediate frequency amplifier 34 that elements such as integrated circuit (IC) 2, ground capacity C101, coupling capacitance C107, C110 are formed.In addition,intermediate frequency amplifier 33 is by transistor Q7, and resistance R 64 is connected with 16/27MHZ selector switch SW2, in put device 34 and then pass through elements such as transistor Q8, diode D12, SW2 is connected with the 16/27MHZ selector switch.

When 16/27MHZ selector switch SW2 is high potential, transistor Q7 conducting, and transistor Q8, diode D12 end, puttingdevice 33 reception frequency ranges in this moment is the intermediate-freuqncy signal of 16MHZ, and with the intermediate-freuqncy signal amplification of being imported, the signal after will amplifying again send band broadnesschangeable demodulation circuit 4.

In like manner, when 16/27MHZ selector switch SW2 is electronegative potential, transistor Q8, diode D12 conducting, transistor Q7 ends, at this moment, putting device 34 reception frequency ranges in the second level is the intermediate-freuqncy signal of 27MHZ, and the intermediate-freuqncy signal of being imported is amplified, and the signal after will amplifying again send band broadnesschangeable demodulation circuit 4.

Band broadnesschangeable demodulation circuit 4 is made ofdemodulator 41 and variable ratio frequencychanger stretch circuit 42, and whereindemodulator 41 connects the output of intermediatefrequency amplifier circuit 3 and the input of variable ratio frequencychanger stretch circuit 42 respectively, and in addition,demodulator 41 also is connected with automatic gain control circuit AGC.

Demodulator 41 is by integrated circuit (IC) 4, elements such ascapacitor C 5, C8, C128, C129, resistance R 21 are formed, receive intermediate-freuqncy signal and this intermediate-freuqncy signal of demodulation of intermediatefrequency amplifier circuit 3 outputs, to obtain good baseband signal, automatic gain control circuit is controlled the gain or the decay of this signal, makes the baseband signal ofdemodulator circuit 41 exportable high-qualitys.

Variable ratio frequencychanger stretch circuit 42 is by capacitor C 130, C131, resistance R 82, R83, diode D13 and provide the elements such as demodulating voltage V13 of this circuit working to form, when 16/27MHZ selector switch SW2 is electronegative potential, demodulating voltage VB control reduces the electric current that flows through diode D13, and change its equiva lent impedance, make thisdemodulator circuit 41 can remain on 16-27MHZ frequency range scope,, can improve the receiving feature of this tuner when wideband to cooperate the antenna size specification; When 16/27MHZ selector switch SW2 is high potential, demodulating voltage VB control increases the electric current that flows through diode D13, and change equiva lent impedance, make thisdemodulator circuit 41 remain on 8-16MHZ frequency range scope, to cooperate the antenna size specification, improve the receiving feature of tuner when narrow frequency, realize goal of the invention.

Claims (4)

1, a kind of satellite receiver turning with band broadness changeable demodulation circuit comprises the radio frequency input circuit of the radiofrequency signal that receives satellite antenna and filtering, amplification; Be subjected to automatic gain control circuit control, with signal amplification, the frequency conversion of the output of radio frequency input circuit and produce the amplification frequency changer circuit of intermediate-freuqncy signal; With amplify the frequency changer circuit output and be connected, be subjected to automatic gain control circuit control, the intermediate-freuqncy signal that receives is amplified and carry out the intermediate frequency amplifier circuit and the reception intermediate frequency amplifier circuit output signal of filtering, amplification with 16MHZ or 27MHZ frequency range respectively and demodulate the demodulator circuit of fundamental frequency signal, described demodulator circuit also is connected with automatic gain control circuit, it is characterized in that:

Described demodulator circuit is a band broadness changeable demodulation circuit, connect and compose by demodulator and the variable ratio frequency changer stretch circuit that makes demodulator remain on 8-27MHZ frequency range scope, the demodulator input connects described intermediate frequency amplifier circuit output, the demodulator output connects variable ratio frequency changer stretch circuit input, and described automatic gain control circuit is connected with described demodulator; Being useful on the control voltage that changes variable ratio frequency changer stretch circuit electric current and circuit equivalent impedance is connected with the variable ratio frequency changer stretch circuit.

2, the satellite receiver turning with band broadness changeable demodulation circuit according to claim 1 is characterized in that; Described radio frequency input circuit is made of two low pass filters, the radio frequency amplifier that is connected with the low pass filter output respectively and the switching circuit of controlling two low pass filter selective reception satellite antenna radiofrequency signals, switching circuit two inputs connect two radio frequency amplifier outputs respectively, the described amplification frequency changer circuit of switching circuit output termination.

3, satellite receiver turning with band broadness changeable demodulation circuit according to claim 1, it is characterized in that: described amplification frequency changer circuit is by tracking filter, the integrated amplification frequency changer circuit of attenuator circuit and the microwave monolithic formation that is linked in sequence, described tracking filter input connects described radio frequency input circuit output, the integrated amplification frequency changer circuit of described microwave monolithic output connects described intermediate frequency amplifier circuit, described automatic gain control circuit is connected with attenuator circuit, and the integrated amplification frequency changer circuit of described microwave monolithic output connects described intermediate frequency amplifier circuit.

4, the satellite receiver turning with band broadness changeable demodulation circuit according to claim 1, it is characterized in that: described intermediate frequency amplifier circuit is linked in sequence and is constituted by first order intermediate frequency amplifier, comb filter, two second level intermediate frequency amplifiers arranged side by side, the input of first order intermediate frequency amplifier connects described amplification frequency changer circuit output, two second level intermediate frequency amplifier outputs also connect described band broadness changeable demodulation circuit input, and described automatic gain control circuit connects described first order intermediate frequency amplifier.

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