CN101478286A - Square wave-sine wave signal converting method and converting circuit - Google Patents

Abstract

The invention discloses a square wave-sine wave signal transformation method comprising the steps as follows: a square wave signal generates N square wave control signals with the same period; the N square wave control signals arrayed in sequence respectively generate N square wave secondary signals; the amplitude sum of the N square wave secondary signals is a; the amplitude of the square wave signal n is a right type; the N square wave secondary signals are processed through superposition to obtain a false sine wave signal; and the false sine wave signal is processed through filtration to obtain a sine wave signal. A square wave-sine wave signal transformation circuit is also disclosed, and the superposition of the N square wave secondary signals in the method is realized by controlling the superposition of current so as to obtain the sine wave signal. The square wave-sine wave signal transformation method and the square wave-sine wave signal transformation circuit avoid adopting a higher order high-frequency filter directly, greatly save the area and the power consumption of a chip, and reduce the design complexity.

Description

Square wave-sine wave signal converting method and change-over circuit

Technical field

The present invention relates to a kind of conversion method of the signal of telecommunication, especially a kind of square wave-sine wave signal converting method.The invention still further relates to a kind of electrical signal conversion circuit, especially a kind of square wave-sine wave signal change-over circuit.

Background technology

In some digital-to-analogue mixed signal system; usually needing that square wave or the signal that is similar to square wave are carried out fundamental frequency extracts; that is to say that needing will be that the numeric type signal intermediate frequency rate of T is that the sine wave of 1/T takes out in the cycle; and high order harmonic component is removed; particularly in the modulated process of some communication system; the regulation that the comparison strictness is all arranged for the transmitting power spectrum; reception or emission with anti-tampering this communication system and other communication system; and the existence of high order harmonic component tends to make modulation spectrum not reach both provisioning requests; as seen, extracting fundamental component from square wave or quasi-square wave is very necessary in some system.

For square wave, except comprising the fundamental component that frequency is 1/T, comprise that also frequency is 3/T in its spectrum component, 5/T ... etc. high order harmonic component, the amplitude of each harmonic is respectively 1/3 of first-harmonic, 1/5 ..., as seen each higher harmonic components has occupied suitable energy in square-wave signal.The way of the most directly removing high order harmonic component adopts filter exactly, but in some systems particularly in the modulating system of radio communication, the frequency of modulation signal is all higher relatively, integrated circuit technology for present main flow under high frequency is to be difficult to realize operational amplifier, therefore can't adopt active pull-up-capacitive filters, and often need to adopt the mutual conductance-capacitive filters of open loop form.Because the linearity of mutual conductance-capacitive filter is lower, even adopt some linearization techniques to improve the linearity, linear properties under high frequency also can worsen, so the effect of this filter process high speed signal is relatively poor, the non-linear meeting of himself makes harmonic wave increase.For square-wave signal, since bigger from the amplitude of the closer each harmonic of first-harmonic, the filtering difficulty further increased.In a word, adopting the mode of the direct filtering of filter need be that cost realizes required filter effect to increase power consumption and exponent number often, and the power consumption of chip, area and design complexities all can increase, and are unfavorable for realizing the product of low-cost and low-power consumption.

Summary of the invention

Technical problem to be solved by this invention provides a kind of square wave-sine wave signal converting method, and the square wave-sine wave signal change-over circuit of this method of realization, can directly generate required sine wave signal, avoid directly adopting the high frequency filter of higher exponent number, save area of chip and power consumption greatly, reduce design complexities.

For solving the problems of the technologies described above, the technical scheme of square wave-sine wave signal converting method of the present invention is to comprise

Identical, duty ratio of N cycle is 50% square wave control signal, and N is the integer greater than 1, and described N square wave control signal arranged in order, and the phase place of a back square wave control signal is than phase lag 1/2N the cycle of its previous square wave control signal;

Generate N square wave secondary signal respectively by N square wave control signal, the amplitude summation of described N square wave secondary signal is a, and the amplitude of n square-wave signal is1≤n≤N wherein;

With described N square wave secondary signal stack, obtain a pseudo sine wave signal, the pseudo sine wave signal is carried out filtering obtain sine wave signal.

The present invention also provides a kind of square wave-sine wave signal change-over circuit, its technical scheme is, comprise sinusoidal wave shaping circuit, described sinusoidal wave shaping circuit comprises the N road constant-current source circuit of arranging in order parallel with one another, N is the integer greater than 1, each road constant-current source circuit comprises positive circuit and the negative circuit that is connected in series, one termination power end of described positive circuit, one end ground connection of negative circuit, described positive circuit comprises a constant-current source and a switch, and described negative circuit comprises a constant-current source and a switch; The size of current that the constant-current source of positive circuit and negative circuit produces in described each road constant-current source circuit equates that direction is identical, the size of current that constant-current source produced in the constant-current source circuit of n road$\mathrm{In}=I(\cos \frac{n-1}{N}\mathrm{\π}-\cos \frac{n}{N}\mathrm{\π}),$Wherein I is the current reference size, 1≤n≤N; Switch in the described constant-current source circuit is respectively by N identical square wave control signal control of cycle, described N square wave control signal arranged in order, the phase place of the square wave control signal in back is than phase lag 1/2N the cycle of its previous square wave control signal, when described square wave control signal is preceding half period, the switch closure of the positive circuit that this square wave control signal is controlled, the switch of negative circuit disconnect, when described square wave control signal was the back half period, the switch of the positive circuit that this square wave control signal is controlled disconnected, the switch closure of negative circuit; Positive circuit all interconnects with the node that negative circuit is connected in the constant-current source circuit of described N road, and as the output of pseudo sine wave signal; Described for the output of sine wave signal is connected with filter amplification circuit, described pseudo sine wave signal processing is become sine wave signal.

The present invention directly generates required sine wave signal by adopting the mode with the square-wave signal stack, has avoided the high frequency filter of the higher exponent number of direct employing, has saved area of chip and power consumption greatly, has reduced design complexities.

Description of drawings

The present invention is further detailed explanation below in conjunction with drawings and Examples:

Fig. 1 is the schematic diagram of square wave-sine wave signal converting method embodiment of the present invention;

Fig. 2 is the spectrogram of middle square-wave signal embodiment illustrated in fig. 1;

Fig. 3 is the spectrogram of middle pseudo sine wave signal embodiment illustrated in fig. 1;

Fig. 4 is the schematic diagram of square wave-sine wave signal change-over circuit of the present invention;

Fig. 5 and Fig. 6 are the schematic diagram of sinusoidal wave shaping circuit embodiment among Fig. 4.

Embodiment

The invention provides a kind of square wave-sine wave signal converting method, comprise

Identical, duty ratio of N cycle is 50% square wave control signal, and N is the integer greater than 1, and described N square wave control signal arranged in order, and the phase place of a back square wave control signal is than phase lag 1/2N the cycle of its previous square wave control signal;

Generate N square wave secondary signal respectively by N square wave control signal, the amplitude summation of described N square wave secondary signal is a, and the amplitude of n square-wave signal is1≤n≤N wherein;

With described N square wave secondary signal stack, obtain a pseudo sine wave signal, the pseudo sine wave signal is carried out filtering obtain sine wave signal.

Described N square wave control signal generated by a square wave control signal.

Figure 1 shows that the schematic diagram of square wave-sine wave signal converting method embodiment of the present invention.It wherein is example with N=8, the phase difference of the signal of these 8 phase places is 1/16 cycle, and just the clock of phase place 8 lags behind 1/16 cycle than the clock of phase place 7, and the clock of phase place 7 lags behind 1/16 cycle than the clock of phase place 6, by that analogy, up to the clock of phase place 1.

In first unit interval in Fig. 1, the clock of 8 phase places is positive half cycle, be 1, this moment is the maximum A of corresponding sinusoidal signal also, in the next unit interval, phase place 1 is a negative half period, all the other phase places are positive half cycle, this moment corresponding sinusoidal signal the B value, wherein the difference of the A-B pairing signal of positive half cycle " counteracting " that can regard the negative half period of phase place 1 and phase place 8 as " subtracts each other " in other words and obtains, enter into the 3rd unit interval after, phase place 1 and 2 is negative half period, all the other phase places are positive half cycle, corresponding sinusoidal signal value is C, and similarly, wherein the difference of the B-C pairing signal of positive half cycle " counteracting " that can regard the negative half period of phase place 2 and phase place 7 as " subtracts each other " in other words and obtains, by that analogy, can obtain as shown in Figure 1 sinusoid signal.According to the amplitude of sinusoidal signal, can obtain A=a, B=0.9239a, C=0.7071a, D=0.3827a.

The sinusoid signal that it is pointed out that such generation is a pseudo-sine signal, because signal is the segmentation ascending manner, but this " saltus step " seen on frequency domain and in fact introduced high order harmonic component.Fig. 2 and Fig. 3 are respectively the spectrograms of square-wave signal and pseudo-sine signal, the harmonic component that this pseudo sine wave is bigger is positioned at 15 and 17 subharmonic places, it is the position of Fig. 3 medium frequency 1.5G and 1.7G, and than the little about 20dB of first-harmonic, such spectrum component is easy to filtering, get final product filtering by general firstorder filter, and total some ghost effects of existence in side circuit, so this high order harmonic component of filtering need not to make especially filter in the reality, parasitic capacitance in the circuit has been enough to this harmonic wave of filtering, and the bigger harmonic component of square-wave signal, as triple-frequency harmonics and quintuple harmonics, as among Fig. 2 less than the position of 500M, it is nearer from fundamental frequency, and only than about the little 10dB of fundamental component, generally need the filter ability filtering of higher exponent number, two compare can find that pseudo-sine signal compares sinusoidal signal and have good spectral purity, and it is simple to have a circuit, the characteristics that power consumption and area are all smaller.

The present invention also provides a kind of square wave-sine wave signal change-over circuit of realizing that above-mentioned square wave-sine wave signal converting method adopts, as Fig. 4, Fig. 5 and shown in Figure 6, comprise sinusoidal wave shaping circuit, described sinusoidal wave shaping circuit comprises the N road constant-current source circuit of arranging in order parallel with one another, N is the integer greater than 1, better N is an even number, each road constant-current source circuit comprises positive circuit and the negative circuit that is connected in series, one termination power end of described positive circuit, one end ground connection of negative circuit, described positive circuit comprises a constant-current source and a switch, and described negative circuit comprises a constant-current source and a switch; The size of current that the constant-current source of positive circuit and negative circuit produces in described each road constant-current source circuit equates that direction is identical, the size of current that constant-current source produced in the constant-current source circuit of n road$\mathrm{In}=I(\cos \frac{n-1}{N}\mathrm{\π}-\cos \frac{n}{N}\mathrm{\π}),$Wherein I is the current reference size, 1≤n≤N; Switch in the described constant-current source circuit is respectively by N identical square wave control signal control of cycle, described N square wave control signal arranged in order, the phase place of the square wave control signal in back is than phase lag 1/2N the cycle of its previous square wave control signal, when described square wave control signal is preceding half period, the switch closure of the positive circuit that this square wave control signal is controlled, the switch of negative circuit disconnect, when described square wave control signal was the back half period, the switch of the positive circuit that this square wave control signal is controlled disconnected, the switch closure of negative circuit; Positive circuit all interconnects with the node that negative circuit is connected in the constant-current source circuit of described N road, and as the output of pseudo sine wave signal; Described for the output of sine wave signal is connected with filter amplification circuit, described pseudo sine wave signal processing is become sine wave signal.

The switch of described positive circuit adopts the PMOS pipe, and the switch of negative circuit adopts the NMOS pipe, the grid of described square wave control signal control PMOS pipe and NMOS pipe.

Described N square wave control signal can be produced by ring oscillator.

Described N square wave control signal also can be produced by delay-locked loop by a square-wave signal.

Described N square wave control signal can also be produced by counter circuit by a square-wave signal.

Fig. 5 and circuit shown in Figure 6 still are example with N=8, can adopt the weighted number weighted-voltage D/A converter of current mode to obtain required sine wave signal, consider from principle, any type of in fact digital to analog converter can be realized sinusoidal wave moulding, but because shaping circuit need carry out frequent plus and minus calculation, this is particularly suitable for current mode digital-to-analog converter, because electric current is realized plus and minus calculation and can directly be connected realization by node, and under the signal speed condition with higher, the speed advantage of current mode digital-to-analog converter is also comparatively obvious.Be similar to the sequential chart of Fig. 1, in first unit interval, 8 clock phases are positive half cycle, so all N pipe switches all disconnect, all P pipe switches are all closed, thereby output current is 8 corresponding electric current sums (I1+I2+I3+I4+I5+I6+I7+I8) of N pipe, in second unit interval, the N of phase place 1 correspondence pipe closure and the P pipe disconnects then, the N pipe of all the other phase place correspondences disconnects and the P pipe is closed, I1=I8, then have the P tube current of phase place 1 correspondence and the N tube current of phase place 8 correspondences to offset, then output current is (I2+I3+I4+I5+I6+I7), by that analogy, I2=I7, I3=I6, I4=I5, then the output current of the 3rd unit interval is (I3+I4+I5+I6), the output current of the 4th unit interval is (I4+I5) ...As seen correspond among Fig. 1,

A＝I1+I2+I3+I4+I5+I6+I7+I8＝2(I1+I2+I3+I4)；

B＝I2+I3+I4+I5+I6+I7＝2(I2+I3+I4)；

C＝I3+I4+I5+I6＝2(I3+I4)；

D＝I4+I5＝2(I4+I5)。

Consider the proportionate relationship of A, B, C, D, obtain easily

I1:I2:I3:I4＝0.0761:0.2168:0.3244:0.3827。

Realize this circuit according to the selected suitable current value of this ratio.

An important application of square wave-sine wave signal converting method provided by the present invention and change-over circuit promptly is a fm transmitter system.Owing to transmit is to adopt frequency modulation(FM), the information of that is to say exists only in the frequency change of modulation signal, therefore fm transmitter system often adopts based on the frequency synthesizer of phase-locked loop and modulates, the output that is to say voltage controlled oscillator promptly is the FM signal after the modulation, generally speaking the voltage controlled oscillator of frequency modulation system is to adopt ring oscillator to constitute, the voltage controlled oscillator of this structure has simplicity of design and the little advantage of area, though phase noise is weaker with respect to the oscillator of electric capacity-inductance resonance, also is enough to satisfy frequency modulation system and has required.In the process of design ring oscillator, in order to improve phase noise, need make oscillator signal have fast as far as possible rise time and fall time, that is to say that signal often is the form near square wave.Suppose that voltage controlled oscillator is output as the ideal square wave of period T, so in this square wave except comprising the fundamental component that frequency is 1/T, comprise that also frequency is 3/T, 5/T, etc. high order harmonic component, the amplitude of each harmonic is respectively 1/3,1/5 of first-harmonic,, as seen each higher harmonic components has occupied suitable energy in square-wave signal.If this signal is directly sent into power amplifier, these high order harmonic components also can be exaggerated so, and these high-order components may enter the frequency range of other radio application, and other signals are caused interference, therefore high order harmonic component must be reduced as far as possible.

Because the frequency range of FM signal is about 100MHz, as previously mentioned, the high frequency filter filtering that is difficult to take high-order takes sinusoidal wave forming technique then can well address this problem from the nearer each harmonic of fundamental frequency.Fig. 4 has provided the frequency modulation system block diagram of a comparatively typical square wave-sine wave signal change-over circuit, utilization produces heterogeneous modulation signal based on the frequency modulator of phase-locked loop, be sent in the sinusoidal wave shaping circuit, the sinusoidal signal of generation can the outer load of driving chip through class buffer amplifier.

The specific implementation of sinusoidal wave shaping circuit as shown in Figure 6, utilize current mirroring circuit to produce each road electric current, the P pipe all adopts the current mirror form, the N pipe then utilizes resistance R and capacitor C to produce a DC feedback, the grid voltage and the drain voltage of N pipe is given, if do not adopt such feedback form, but N pipe and P pipe all are connected into the current mirror form that high resistant is exported, then output node is the high resistant node, can make the DC level instability, cause circuit malfunction, so the such processing of N pipe can be played the effect of stable DC level.Under the enough big situation of RC value, only constitute direct current and low frequency feedback, and high-frequency signal can not feed back, therefore the N pipe also can be regarded as and the same current mirror form of P pipe under high frequency, the high frequency output impedance that is the two is all bigger, can guarantee the output performance of current signal.Because this circuit is based on current mode digital-to-analog converter, therefore output impedance is bigger, driving force relatively a little less than, generally need by the outer load of buffer amplifier circuit driving chip, because there is certain input capacitance in buffer amplifier circuit, this electric capacity also can be used for the pseudo sine wave filter is comparatively pure sine wave just, in amplifier, also some simple filter circuits can be set as required in addition, compare with the method for direct employing filter, here only need the very harmonic wave of high order of filtering, therefore be easy to realize.Finally reach well behaved sinusoidal wave moulding purpose, and signal can have been amplified the corresponding load of driving through buffering.

In sum, the present invention directly generates required sine wave signal by adopting the mode with the square-wave signal stack, has avoided the high frequency filter of the higher exponent number of direct employing, has saved area of chip and power consumption greatly, has reduced design complexities.

Claims (8)

1. a square wave-sine wave signal converting method is characterized in that, comprises

Identical, duty ratio of N cycle is 50% square wave control signal, and N is the integer greater than 1, and described N square wave control signal arranged in order, and the phase place of a back square wave control signal is than phase lag 1/2N the cycle of its previous square wave control signal;

Generate N square wave secondary signal respectively by N square wave control signal, the amplitude summation of described N square wave secondary signal is a, and the amplitude of n square-wave signal is$\frac{a}{2}(\cos \frac{n-1}{N}\mathrm{\π}-\cos \frac{n}{N}\mathrm{\π}),$1≤n≤N wherein;

With described N square wave secondary signal stack, obtain a pseudo sine wave signal, the pseudo sine wave signal is carried out filtering obtain sine wave signal.

2. square wave-sine wave signal converting method according to claim 1 is characterized in that, described N square wave control signal generated by a square wave control signal.

3. square wave-sine wave signal change-over circuit of realizing that square wave-sine wave signal converting method as claimed in claim 1 adopted, it is characterized in that, comprise sinusoidal wave shaping circuit, described sinusoidal wave shaping circuit comprises the N road constant-current source circuit of arranging in order parallel with one another, N is the integer greater than 1, each road constant-current source circuit comprises positive circuit and the negative circuit that is connected in series, one termination power end of described positive circuit, one end ground connection of negative circuit, described positive circuit comprises a constant-current source and a switch, and described negative circuit comprises a constant-current source and a switch; The size of current that the constant-current source of positive circuit and negative circuit produces in described each road constant-current source circuit equates that direction is identical, the size of current that constant-current source produced in the constant-current source circuit of n road$\mathrm{In}=I(\cos \frac{n-1}{N}\mathrm{\π}-\cos \frac{n}{N}\mathrm{\π}),$Wherein I is the current reference size, 1≤n≤N; Switch in the described constant-current source circuit is respectively by N identical square wave control signal control of cycle, described N square wave control signal arranged in order, the phase place of the square wave control signal in back is than phase lag 1/2N the cycle of its previous square wave control signal, when described square wave control signal is preceding half period, the switch closure of the positive circuit that this square wave control signal is controlled, the switch of negative circuit disconnect, when described square wave control signal was the back half period, the switch of the positive circuit that this square wave control signal is controlled disconnected, the switch closure of negative circuit; Positive circuit all interconnects with the node that negative circuit is connected in the constant-current source circuit of described N road, and as the output of pseudo sine wave signal; Described for the output of sine wave signal is connected with filter amplification circuit, described pseudo sine wave signal processing is become sine wave signal.

4. square wave according to claim 3-sine wave signal change-over circuit is characterized in that, the switch of described positive circuit adopts the PMOS pipe, and the switch of negative circuit adopts the NMOS pipe, the grid of described square wave control signal control PMOS pipe and NMOS pipe.

5. square wave according to claim 3-sine wave signal change-over circuit is characterized in that, described N is an even number.

6. square wave according to claim 3-sine wave signal change-over circuit is characterized in that, described N square wave control signal produced by ring oscillator.

7. square wave according to claim 3-sine wave signal change-over circuit is characterized in that, described N square wave control signal produced by delay-locked loop by a square-wave signal.

8. square wave according to claim 3-sine wave signal change-over circuit is characterized in that, described N square wave control signal produced by counter circuit by a square-wave signal.

Images