Pre-demodulation circuit and signal receiving end

Abstract

The invention discloses a pre-demodulation circuit and a signal receiving end, and relates to the technical field of communication. The pre-demodulation circuit comprises at least one control unit, at least one amplification coefficient adjusting unit, a first impedance unit, a second impedance unit and an amplification unit, the input ends of the amplification coefficient adjusting units and the input ends of the control units are connected with a differential signal input end, the output end of each amplification coefficient adjusting unit is connected with the positive input end or the negative input end of the amplification unit, and the output end of each control unit is connected with the control end of one amplification coefficient adjusting unit. The control unit is used for controlling the equivalent impedance of the amplification coefficient adjusting unit according to a differential signal provided by the differential signal input end; the first impedance unit is connected between the negative input end and the output end of the amplification unit, the input end of the second impedance unit is used for inputting direct-current voltage, and the output end of the second impedance unit is connected with the positive input end of the amplification unit. The signal-to-noise ratio of the baseband signal is increased, and the accuracy of signal transmission is improved.

Description

Technical Field

[0001] The embodiments of the present invention relate to the field of communication technology, and in particular to a pre-demodulation circuit and a signal receiving end. Background Art

[0002] With the development of society, electronic products are becoming more and more popular, and charging electronic products has become inevitable. Wireless charging technology has brought great convenience to the charging of electronic products, among which wireless communication plays a vital role. In the process of wireless communication, the original signal often has a low frequency and is not suitable for direct wireless transmission. Therefore, at the transmitting end, the original signal needs to be converted into a signal form suitable for channel transmission through modulation technology. At the receiving end, the received signal is restored to the original signal through demodulation technology, thereby realizing the transmission of information.

[0003] When the modulation technology of the transmitter is amplitude modulation (AM), the modulated signal is an envelope signal. The depth of the envelope curve is the amplitude of the baseband signal. When the receiver demodulates the received modulated signal, it can be amplified or reduced through the pre-demodulation circuit. When the baseband signal amplitude of the modulated signal is small, the envelope curve is relatively shallow and the modulation depth of the signal is relatively small. After the pre-demodulation circuit, the modulation depth of the signal remains the same as before, that is, the modulation depth of the signal is still relatively small, which makes the signal-to-noise ratio of the signal after demodulation relatively low, reducing the accuracy of signal transmission. Summary of the invention

[0004] The present invention provides a pre-demodulation circuit and a signal receiving end, so as to improve the signal-to-noise ratio of the demodulated signal and improve the accuracy of signal transmission.

[0005] In a first aspect, an embodiment of the present invention provides a pre-demodulation circuit, comprising at least one control unit, at least one amplification factor adjustment unit, a first impedance unit, a second impedance unit and an amplification unit;

[0006] The input end of the amplification factor adjustment unit and the input end of the control unit are connected to the differential signal input end, the output end of each amplification factor adjustment unit is connected to the positive input end or the negative input end of the amplification unit, the output end of each control unit is connected to the control end of an amplification factor adjustment unit, and the control unit is used to control the equivalent impedance of the amplification factor adjustment unit according to the differential signal provided by the differential signal input end; the first impedance unit is connected between the negative input end and the output end of the amplification unit, the input end of the second impedance unit is used to input a DC voltage, and the output end of the second impedance unit is connected to the positive input end of the amplification unit.

[0007] Optionally, the amplification factor adjustment unit includes an adjustment transistor; the first electrode of the adjustment transistor and the input end of the control unit are connected to the differential signal input end, the substrate of the adjustment transistor is connected to the output end of the control unit, and the second electrode of the adjustment transistor is connected to the positive input end or the negative input end of the amplification unit; the control unit is used to adjust the equivalent impedance of the adjustment transistor according to the differential signal.

[0008] Optionally, the differential signal input terminal includes a first differential signal input terminal and a second differential signal input terminal;

[0009] At least one of the amplification factor adjustment units includes a first amplification factor adjustment unit and a second amplification factor adjustment unit; at least one of the control units includes a first control unit and a second control unit; the first amplification factor adjustment unit includes a first adjustment transistor; the first electrode of the first adjustment transistor and the input end of the first control unit are connected to the first differential signal input end, the substrate of the first adjustment transistor is connected to the output end of the first control unit, and the second electrode of the first adjustment transistor is connected to the positive input end of the amplification unit; the first control unit is used to adjust the equivalent impedance of the first adjustment transistor according to the first differential signal; the second amplification factor adjustment unit includes a second adjustment transistor; the first electrode of the second adjustment transistor and the input end of the second control unit are connected to the second differential signal input end, the substrate of the second adjustment transistor is connected to the output end of the second control unit, and the second electrode of the second adjustment transistor is connected to the negative input end of the amplification unit; the second control unit is used to adjust the equivalent impedance of the second adjustment transistor according to the second differential signal.

[0010] Optionally, the first regulating transistor and the second regulating transistor are regulating transistors of opposite types; the first electrode of the first regulating transistor and the first electrode of the second regulating transistor are both sources or drains, or the first regulating transistor and the second regulating transistor are regulating transistors of the same type; the first electrode of the first regulating transistor is a drain or a source, and the first electrode of the second regulating transistor is a source or a drain; the gate of the regulating transistor is connected to the drain.

[0011] Optionally, the amplification factor adjustment unit also includes a first resistor; the first resistor is connected in series between the second electrode of the adjustment transistor and the positive input terminal of the amplification unit, or between the second electrode of the adjustment transistor and the negative input terminal of the amplification unit.

[0012] Optionally, the amplification factor adjustment unit also includes a switch module and a second resistor, the first input terminal of the switch module and the first end of the second resistor are connected to the differential signal input terminal, the second input terminal of the switch module is connected to the reference signal input terminal, the enable terminal of the switch module is connected to the enable signal input terminal, the output terminal of the switch module is connected to the first electrode of the adjustment transistor, the second electrode of the adjustment transistor and the second end of the second resistor are connected to the positive input terminal or the negative input terminal of the amplification unit; the switch module is used to connect the differential signal input terminal and the first electrode of the adjustment transistor when the enable signal provided at the enable signal input terminal is valid and the differential signal and the parameter signal provided at the reference signal input terminal meet a preset condition.

[0013] Optionally, the switch module includes a comparator and a switch transistor;

[0014] The first input terminal of the comparator and the first electrode of the switching transistor serve as the first input terminal of the switching module, the enable terminal of the comparator serves as the enable terminal of the switching module, the second input terminal of the comparator serves as the second input terminal of the switching module, the output terminal of the comparator is connected to the gate of the switching transistor, and the second electrode of the switching transistor serves as the output terminal of the switching module.

[0015] Optionally, the control unit includes an amplifier, a third resistor and a fourth resistor;

[0016] The positive input terminal of the amplifier is connected to the differential signal input terminal, the negative input terminal of the amplifier is connected to the first end of the third resistor and the first end of the fourth resistor, the second end of the third resistor is grounded, and the second end of the fourth resistor and the output terminal of the amplifier are connected to the control terminal of the amplification factor adjustment unit.

[0017] Optionally, the control unit includes a voltage follower module and a resistance adjustment module;

[0018] The input end of the voltage follower module and the first input end of the resistance adjustment module are connected to the differential signal input end, the output end of the voltage follower module is connected to the control end of the resistance adjustment module, the second input end of the resistance adjustment module is connected to the positive input end or the negative input end of the amplification unit, and the output end of the resistance adjustment module is connected to the control end of the amplification factor adjustment unit; the voltage follower module is used to adjust the equivalent impedance of the resistance adjustment module according to the differential signal.

[0019] In the second aspect, an embodiment of the present invention further provides a signal receiving end, comprising an analog-to-digital conversion circuit, a demodulation circuit and the pre-demodulation circuit described in the first aspect; the pre-demodulation circuit is connected to the analog-to-digital conversion circuit, and the analog-to-digital conversion circuit is connected to the demodulation circuit; the pre-demodulation circuit is used to gain the differential signal to form a pre-demodulated signal; the analog-to-digital conversion circuit is used to perform analog-to-digital conversion on the pre-demodulated signal to form a digital signal; and the demodulation circuit is used to demodulate the digital signal.

[0020] The technical solution of the embodiment of the present invention controls the equivalent impedance of the amplification factor adjustment unit according to the differential signal through the control unit, so that the equivalent impedance of the amplification factor adjustment unit can change nonlinearly according to the size of the differential signal, thereby increasing the gain when the differential signal is relatively large, and reducing the gain when the differential signal is relatively small, thereby increasing the amplitude of the envelope signal, thereby increasing the signal-to-noise ratio of the baseband signal after the envelope signal is demodulated, thereby improving the accuracy of signal transmission. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 A schematic diagram of a demodulation link structure provided for related technologies;

[0022] Figure 2 A structural schematic diagram of a pre-demodulation circuit provided for related technology;

[0023] Figure 3 A waveform diagram of a modulated signal provided for related technology;

[0024] Figure 4 A schematic diagram of the structure of a pre-demodulation circuit provided by an embodiment of the present invention;

[0025] Figure 5 A schematic diagram of the structure of another pre-demodulation circuit provided by an embodiment of the present invention;

[0026] Figure 6 A schematic diagram for comparing waveforms of modulated signals amplified by different pre-demodulation circuits provided in an embodiment of the present invention;

[0027] Figure 7 A waveform comparison diagram of another type of pre-demodulation circuit amplifying a modulated signal provided by an embodiment of the present invention;

[0028] Figure 8 A schematic diagram of the structure of another pre-demodulation circuit provided by an embodiment of the present invention;

[0029] Fig. 9 A schematic diagram of the structure of a control unit provided by an embodiment of the present invention;

[0030] Fig.10A schematic diagram of the structure of another control unit provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0031] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for ease of description, only parts related to the present invention, rather than all structures, are shown in the accompanying drawings.

[0032] Figure 1 A schematic diagram of a demodulation link structure provided for related technologies, Figure 2 A schematic diagram of the structure of a pre-demodulation circuit provided in the related art. Figure 1 and Figure 2 As shown, during the wireless communication process, the signal receiving end may include a receiving coil 100, a frequency selection circuit 101, a pre-demodulation circuit 102, an analog-to-digital conversion circuit 103 and a demodulation circuit 104. The receiving coil 100 receives the modulated signal sent by the signal transmitting end. The modulated signal may be a modulated signal formed by AM modulation of an analog signal. The frequency selection circuit 101 performs frequency selection on the modulated signal to obtain a modulated signal of a preset frequency. Then the pre-demodulation circuit 102 reduces and filters the modulated signal according to a certain ratio to realize pre-demodulation of the modulated signal and outputs it to the analog-to-digital conversion circuit 103. The analog-to-digital conversion circuit 103 performs digital-to-analog conversion on the pre-demodulated signal and outputs it to the demodulation circuit 104. The demodulation circuit 104 demodulates the pre-demodulated signal to obtain a baseband signal to realize signal transmission. The demodulation circuit 104 may demodulate the pre-demodulated signal by amplitude shift keying (ASK). When the pre-demodulation circuit 102 scales down and filters the modulated signal, the pre-demodulation circuit 102 has a fixed low-frequency gain, which is the ratio of the second voltage-divider resistor R2 to the first voltage-divider resistor R1, that is, r2 / r1. Among them, r2 is the resistance value of the second voltage-divider resistor R2, and r1 is the resistance value of the first voltage-divider resistor R1. At this time, the pre-demodulation circuit 102 can make a linear change of the modulated signal with the same gain. When the amplitude of the envelope curve is shallow, the modulation depth of the signal after passing through the pre-demodulation circuit is still not obvious, and the ratio of the envelope amplitude to the carrier amplitude remains unchanged. If the input signal of the analog-to-digital conversion circuit 103 is full swing at this time, it is equivalent to the conversion of the carrier close to the full swing conversion, and the amplitude change of the baseband signal, that is, the amplitude of the envelope curve is small, so that the conversion signal-to-noise ratio of the modulated signal is higher, but relative to the required baseband signal, the signal-to-noise ratio will be significantly lower than the signal-to-noise ratio of the overall signal, reducing the accuracy of signal transmission. Exemplary, Figure 3 A waveform diagram of a modulated signal provided for related technology. Figure 3As shown in the figure, the carrier frequency is 360kHz and the baseband signal frequency is 20kHz. The amplitude of the envelope curve of the modulated signal is relatively shallow.

[0033] In view of the above technical problem, an embodiment of the present invention provides a pre-demodulation circuit. Figure 4 Schematic diagram of a pre-demodulation circuit provided by an embodiment of the present invention. Figure 4 As shown, the pre-demodulation circuit includes at least one control unit 110, at least one gain adjustment unit 120, a first impedance unit 130, a second impedance unit 140 and an amplifying unit 150; the input end of the gain adjustment unit 120 and the input end of the control unit 110 are connected to the differential signal input end Vi, the output end of each gain adjustment unit 120 is connected to the positive input end V+ or the negative input end V- of the amplifying unit 150, the output end of each control unit 110 is connected to the control end Vb of an gain adjustment unit 120, and the control unit 110 is used to control the equivalent impedance of the gain adjustment unit 120 according to the differential signal provided by the differential signal input end Vi; the first impedance unit 130 is connected between the negative input end V- and the output end VOUT of the amplifying unit 150, the input end of the second impedance unit 140 is used to input a DC voltage Vc, and the output end of the second impedance unit 140 is connected to the positive input end V+ of the amplifying unit 150.

[0034] Specifically, the differential signal input terminal Vi may include a first differential signal input terminal Vip and a second differential signal input terminal Vin. The first differential signal input terminal Vip is used to input a first differential signal, for example, a positive voltage signal, and the second differential signal input terminal Vin is used to input a second differential signal, for example, a negative voltage signal. The first differential signal and the second differential signal are voltage signals with equal amplitudes and opposite signs. The differential signal input to the differential signal input terminal Vi is a modulated signal, for example, a modulated signal formed by AM modulation. Figure 4The example in the figure shows that the amplification factor adjustment unit 120 includes two, namely, a first amplification factor adjustment unit 121 and a second amplification factor adjustment unit 122. The first amplification factor adjustment unit 121 is connected between the first differential signal input terminal Vip and the positive input terminal V+ of the amplification unit 150, and the second amplification factor adjustment unit 122 is connected between the second differential signal input terminal Vin and the negative input terminal V- of the amplification unit 150. The control unit 110 includes a first control unit 111 and a second control unit 112. The input terminal of the first control unit 111 is connected to the first differential signal input terminal Vip, and the output terminal is connected to the control terminal Vb1 of the first amplification factor adjustment unit 121, so as to control the equivalent impedance of the first amplification factor adjustment unit 121. The input terminal of the second control unit 112 is connected to the second differential signal input terminal Vin, and the output terminal is connected to the control terminal Vb2 of the second amplification factor adjustment unit 122, so as to control the equivalent impedance of the second amplification factor adjustment unit 122. When the differential signal is input to the control unit 110, the control unit 110 may control the equivalent impedance of the amplification factor adjustment unit 120 according to the size of the differential signal. Exemplarily, when the input differential signal increases, the control unit 110 may control the equivalent impedance of the amplification factor adjustment unit 120 to decrease. When the input differential signal decreases, the control unit 110 may control the equivalent impedance of the amplification factor adjustment unit 120 to increase.

[0035] The amplification unit 150 has an amplification function. Exemplarily, the amplification unit 150 may include an amplifier. The first impedance unit 130 is connected between the negative input terminal V- and the output terminal VOUT of the amplification unit 150, the input terminal of the second impedance unit 140 is used to input the DC voltage Vc, and the output terminal of the second impedance unit 140 is connected to the positive input terminal V+ of the amplification unit 150. The bandwidth of the pre-demodulation circuit can be adjusted by the first impedance unit 130 and the second impedance unit 140, and the DC component output by the output terminal VOUT of the pre-demodulation circuit can be adjusted by the DC voltage Vc. Exemplarily, the first impedance unit 130 may include a first filter resistor R31 and a first capacitor C1 connected in parallel, and the second impedance unit 140 may include a second filter resistor R32 and a second capacitor C2 connected in parallel, that is, the first end of the first filter resistor R31 and the first end of the first capacitor C1 are connected to the negative input terminal V- of the amplification unit 150, and the second end of the first filter resistor R31 and the second end of the first capacitor C1 are connected to the output terminal VOUT of the amplification unit 150. The first end of the second filter resistor R32 and the first end of the second capacitor C2 are used to input the DC voltage Vc, and the second end of the second filter resistor R32 and the second end of the second capacitor C2 are connected to the positive input terminal V+ of the amplifier unit 150. At this time, according to the "virtual short" and "virtual open" principles of the amplifier, formula (1) can be determined:

[0036]

[0037] Wherein, Vn is the voltage of the negative input terminal V- of the amplifying unit 150, and Vp is the voltage of the positive input terminal V+ of the amplifying unit 150. When the capacitance values ​​of the first capacitor C1 and the second capacitor C2 are equal, and the resistance values ​​of the first filter resistor R31 and the second filter resistor R32 are equal, according to the KCL and KVL principles of the circuit, equations (2) and (3) can be determined:

[0038]

[0039] Wherein, vip is the first differential signal provided by the first differential signal input terminal Vip, Vc is a DC voltage, r3 is the resistance of the first filter resistor R31, 1 / sc1 is the equivalent impedance of the first capacitor C1, and rc is the equivalent impedance of the amplification factor adjustment unit 120;

[0040]

[0041] Wherein, vin is the second differential signal provided by the second differential signal input terminal Vin, vout is the pre-demodulated voltage output by the output terminal VOUT of the amplification unit 150, r3 is the resistance value of the first filter resistor R31, 1 / sc1 is the equivalent impedance of the first capacitor C1, and rc is the equivalent impedance of the amplification factor adjustment unit 120;

[0042] Therefore, according to equation (1), equation (2) and equation (3), equation (4) is determined:

[0043]

[0044] It can be seen that the bandwidth of the pre-demodulation circuit is 1 / 2πr3c1, which is independent of the equivalent resistance of the amplification factor adjustment unit 120, and the low-frequency gain of the pre-demodulation circuit is r3 / rc. When the input differential signal increases, the control unit 110 controls the equivalent impedance rc of the amplification factor adjustment unit 120 to decrease, so that the low-frequency gain r3 / rc of the pre-demodulation circuit increases. When the input differential signal decreases, the control unit 110 controls the equivalent impedance rc of the amplification factor adjustment unit 120 to increase, so that the low-frequency gain r3 / rc of the pre-demodulation circuit decreases. Therefore, the nonlinear amplification adjustment can be performed on the differential signal according to its size. After the envelope signal passes through the pre-demodulation circuit, the amplitude of the envelope signal increases, so that after the envelope signal is demodulated, the signal-to-noise ratio of the baseband signal is increased, thereby improving the accuracy of signal transmission.

[0045] The technical solution of this embodiment controls the equivalent impedance of the amplification factor adjustment unit according to the differential signal through the control unit, so that the equivalent impedance of the amplification factor adjustment unit can change nonlinearly according to the size of the differential signal, thereby increasing the gain when the differential signal is relatively large, and reducing the gain when the differential signal is relatively small, thereby increasing the amplitude of the envelope signal, thereby increasing the signal-to-noise ratio of the baseband signal after the envelope signal is demodulated, thereby improving the accuracy of signal transmission.

[0046] Figure 5 FIG. 1 is a schematic diagram of another pre-demodulation circuit provided by an embodiment of the present invention. Figure 5 As shown, the amplification factor adjustment unit 120 includes an adjustment transistor M; the first electrode of the adjustment transistor M and the input end of the control unit 110 are connected to the differential signal input end Vi, the substrate of the adjustment transistor M is connected to the output end of the control unit 110, and the second electrode of the adjustment transistor M is connected to the positive input end V+ or the negative input end V- of the amplification unit 150; the control unit 110 is used to adjust the equivalent impedance of the adjustment transistor M according to the differential signal.

[0047] Specifically, Figure 5 The example in FIG1 shows that the regulating transistor M is an N-type transistor. The substrate of the regulating transistor M serves as the control terminal Vb of the gain adjustment unit 120 and is connected to the output terminal of the control unit 110. When the differential signal increases, the control unit 110 can control the substrate potential of the regulating transistor M to increase. According to equations (5) and (6), when the substrate potential of the regulating transistor M increases, the threshold voltage of the regulating transistor M decreases, and the on-resistance of the regulating transistor M decreases. The equivalent impedance rc of the gain adjustment unit 120 includes the on-resistance of the regulating transistor M. When the on-resistance of the regulating transistor M decreases, the equivalent impedance rc of the gain adjustment unit 120 decreases, and the low-frequency gain of the pre-demodulation circuit increases. On the contrary, when the differential signal decreases, the control unit 110 can control the substrate potential of the regulating transistor M to decrease. According to equations (5) and (6), when the substrate potential of the regulating transistor M decreases, the threshold voltage of the regulating transistor M increases, and the on-resistance of the regulating transistor M increases, so that the equivalent impedance rc of the amplification factor adjusting unit 120 increases, and the low-frequency gain of the pre-demodulation circuit decreases. Therefore, the nonlinear amplification adjustment of the differential signal can be performed according to its size. After the envelope signal passes through the pre-demodulation circuit, the amplitude of the envelope signal increases, so that after the envelope signal is demodulated, the signal-to-noise ratio of the baseband signal is increased, thereby improving the accuracy of signal transmission.

[0048]

[0049] Wherein, Vth is the threshold voltage of the regulating transistor M, Vth0 is the threshold voltage when the voltage difference between the source and the substrate of the regulating transistor M is 0, VSB is the voltage difference between the source and the substrate of the regulating transistor M, γ is the substrate bias coefficient of the regulating transistor M, is the built-in potential of the adjusting transistor M, rm is the equivalent resistance of the adjusting transistor M, Vgs is the gate-source voltage difference of the adjusting transistor M, W / L is the channel width-to-length ratio of the adjusting transistor M, Cox is the equivalent capacitance of the gate oxide layer of the adjusting transistor M, and μ is the electron mobility of the adjusting transistor M.

[0050] For example, Figure 6 A waveform comparison diagram of different pre-demodulation circuits amplifying modulated signals provided by an embodiment of the present invention, Figure 7 A waveform comparison diagram of another embodiment of the present invention for different pre-demodulation circuits amplifying modulated signals. Figure 6 The original modulated signal and Figure 7 The corresponding pre-demodulated signal after the linear change in is Figure 2 The waveform after the pre-demodulation circuit provided pre-demodulates the modulated signal, Figure 6 The nonlinear amplification signal and Figure 7 The corresponding pre-demodulated signal after the nonlinear change in is Figure 5 The waveform after the pre-demodulation circuit provided pre-demodulates the modulated signal. Figure 6 and Figure 7 As shown, after the modulated signal is pre-demodulated by the pre-demodulation circuit provided by the embodiment of the present invention, the amplitude of the envelope signal increases, so that after the envelope signal is demodulated, the signal-to-noise ratio of the baseband signal is increased, thereby improving the accuracy of signal transmission.

[0051] For example, continue to refer to Figure 5, the differential signal input terminal Vi includes a first differential signal input terminal Vip and a second differential signal input terminal Vin. At least one amplification factor adjustment unit 120 includes a first amplification factor adjustment unit 121 and a second amplification factor adjustment unit 122; at least one control unit 110 includes a first control unit 111 and a second control unit 112; the first amplification factor adjustment unit 121 includes a first adjustment transistor NM1; the first electrode of the first adjustment transistor NM1 and the input end of the first control unit 111 are connected to the first differential signal input terminal Vip, the substrate Vb1 of the first adjustment transistor NM1 is connected to the output end of the first control unit 111, and the second electrode of the first adjustment transistor NM1 is connected to the positive input end of the amplification unit 150 V+; the first control unit 111 is used to adjust the equivalent impedance of the first regulating transistor V+ according to the first differential signal; the second amplification factor adjusting unit 122 includes a second regulating transistor NM2; the first electrode of the second regulating transistor NM2 and the input end of the second control unit 112 are connected to the second differential signal input end Vin, the substrate Vb2 of the second regulating transistor NM2 is connected to the output end of the second control unit 112, and the second electrode of the second regulating transistor NM2 is connected to the negative input end V- of the amplification unit 150; the second control unit 112 is used to adjust the equivalent impedance of the second regulating transistor NM2 according to the second differential signal.

[0052] Specifically, the number of control units 110 is equal to the number of amplification factor adjustment units 120. When the amplification factor adjustment units 120 include two, the control unit 110 also includes two, each controlling the equivalent impedance of an amplification factor adjustment unit 120. When the control unit 110 controls the equivalent impedance of the amplification factor adjustment unit 120, the equivalent impedance of the first adjustment transistor NM1 and the second adjustment transistor NM2 can be controlled to be equal, so that the equivalent impedance of the first amplification factor adjustment unit 121 and the second amplification factor adjustment unit are equal, thereby simplifying the calculation process of the low-frequency gain of the pre-demodulation circuit and simplifying the adjustment process of the low-frequency gain of the pre-demodulation circuit.

[0053] It should be noted that, in other embodiments, the equivalent impedances of the first amplification factor adjustment unit 121 and the second amplification factor adjustment unit can be set to be unequal. Similarly, the low-frequency gain of the pre-demodulation circuit can be adjusted by changing the equivalent impedances of the first amplification factor adjustment unit 121 and the second amplification factor adjustment unit, which will not be repeated here.

[0054] Continue to refer Figure 5 The first regulating transistor NM1 and the second regulating transistor NM2 are transistors of the same type. The first electrode of the first regulating transistor NM1 is a drain or a source, and the first electrode of the second regulating transistor NM2 is a source or a drain. The gate of the regulating transistor M is connected to the drain.

[0055] Specifically, Figure 5 exemplarily shows that the first regulating transistor NM1 and the second regulating transistor NM2 are both N-type transistors. At this time, the first electrode of the first regulating transistor NM1 can be set as a drain electrode and connected to the gate of the first regulating transistor NM1. When the first regulating transistor NM1 is not turned on, there is no current between the first differential signal input terminal Vip and the positive input terminal V+ of the amplifying unit 150, and between the DC voltage input terminal and the positive input terminal V+ of the amplifying unit 150, so that the second electrode potential of the first regulating transistor NM1 is equal to the DC voltage Vc. When the first differential signal is greater than the second differential signal, the first electrode of the first regulating transistor NM1 can be set as a drain electrode, and the first electrode of the second regulating transistor NM2 is a source electrode. When the voltage of the first differential signal is greater than the DC voltage Vc and the threshold voltage of the first regulating transistor NM1, the first regulating transistor NM1 is turned on, and the first regulating transistor NM1 is in a saturated state. As the gate-source voltage increases, the current of the first regulating transistor NM1 increases exponentially, and the equivalent resistance of the first regulating transistor NM1 decreases nonlinearly. At this time, the substrate potential of the first regulating transistor NM1 can be adjusted by the first control unit 111, and then the equivalent impedance of the first regulating transistor NM1 can be adjusted according to equations (5) and (6), thereby realizing the nonlinear gain of the pre-demodulation circuit, increasing the signal-to-noise ratio of the baseband signal, and thus improving the accuracy of signal transmission. When the voltage of the second differential signal is less than the difference between the output voltage provided by the output terminal VOUT of the amplification unit 150 and the threshold voltage of the second regulating transistor NM2, the second regulating transistor NM2 is turned on, and the second regulating transistor NM2 is in a saturation state. At this time, the substrate potential of the second regulating transistor NM2 can be adjusted by the second control unit 112, and then the equivalent impedance of the second regulating transistor NM2 can be adjusted according to equations (5) and (6), thereby realizing the nonlinear gain of the pre-demodulation circuit, increasing the signal-to-noise ratio of the baseband signal, and thus improving the accuracy of signal transmission.

[0056] In some embodiments, when the first differential signal is smaller than the second differential signal, the first electrode of the first regulating transistor NM1 can be set as the source, and the first electrode of the second regulating transistor NM2 can be set as the drain. The equivalent impedance of the first regulating transistor NM1 and the second regulating transistor NM2 can also be adjusted through the above process, which will not be repeated here.

[0057] In some embodiments, the first regulating transistor and the second regulating transistor are regulating transistors of opposite types; the first electrode of the first regulating transistor and the first electrode of the second regulating transistor are both sources or drains.

[0058] Specifically, when the types of the first regulating transistor and the second regulating transistor are opposite, for example, the first regulating transistor is an N-type transistor, the second regulating transistor is a P-type transistor, and the first electrode of the first regulating transistor and the first electrode of the second regulating transistor are both drain electrodes. Alternatively, the first regulating transistor is a P-type transistor, the second regulating transistor is an N-type transistor, and the first electrode of the first regulating transistor and the first electrode of the second regulating transistor are both sources. At this time, the conduction state of the first regulating transistor and the second regulating transistor can also be controlled by the first differential signal and the second differential signal, so that the equivalent impedance of the first regulating transistor and the second regulating transistor can be controlled, and then the low-frequency gain of the pre-demodulation circuit can be adjusted.

[0059] Continue to refer Figure 5 The amplification factor adjustment unit 120 also includes a first resistor R4; the first resistor R4 is connected in series between the second electrode of the adjustment transistor M and the positive input terminal V+ of the amplification unit 150, or between the second electrode of the adjustment transistor M and the negative input terminal V- of the amplification unit 150.

[0060] Specifically, the first resistor R4 may be a resistor of a fixed resistance. By connecting the first resistor R4 in series between the adjusting transistor NM1 and the amplifying unit 150, the resistance reliability of the amplification factor adjusting unit 120 may be ensured, and the order of magnitude of the low-frequency gain of the pre-demodulation circuit may be limited. Exemplarily, when the amplification factor adjusting unit 120 includes a first amplification factor adjusting unit 121 and a second amplification factor adjusting unit 122, the first amplification factor adjusting unit 121 and the second amplification factor adjusting unit 122 both include a first resistor R4, the first resistor R4 in the first amplification factor adjusting unit 121 is connected between the second electrode of the first adjusting transistor NM1 and the positive input terminal V+ of the amplifying unit 150, and is used to adjust the equivalent impedance of the first amplification factor adjusting unit 121, and the first resistor R4 in the second amplification factor adjusting unit 122 is connected between the second electrode of the second adjusting transistor NM2 and the negative input terminal V- of the amplifying unit 150, and is used to adjust the equivalent impedance of the second amplification factor adjusting unit 122.

[0061] Figure 8 FIG. 1 is a schematic diagram of another pre-demodulation circuit provided by an embodiment of the present invention. Figure 8As shown, the amplification factor adjustment unit 120 also includes a switch module 123 and a second resistor R5, the first input end of the switch module 123 and the first end of the second resistor R5 are connected to the differential signal input end Vi, the second input end of the switch module 123 is connected to the reference signal input end VREF, the enable end of the switch module 123 is connected to the enable signal input end EN, the output end of the switch module 123 is connected to the first electrode of the adjustment transistor M, the second electrode of the adjustment transistor M and the second end of the second resistor R5 are connected to the positive input end V+ or the negative input end V- of the amplification unit 150; the switch module 123 is used to connect the differential signal input end Vi and the first electrode of the adjustment transistor M when the enable signal provided by the enable signal input end EN is valid and the differential signal and the parameter signal provided by the reference signal input end VREF meet the preset conditions.

[0062] Specifically, the enable signal provided by the enable signal input terminal EN can be set according to the envelope amplitude of the modulated signal. When the envelope amplitude of the modulated signal is obvious, the enable signal can be invalidated, the switch module 123 does not work, and the differential signal input terminal Vi and the first pole of the regulating transistor M cannot be connected. The differential signal is directly output to the positive input terminal V+ or the negative input terminal V- of the amplification unit 150 through the second resistor R5. At this time, the pre-demodulation circuit has a fixed gain. When the envelope amplitude of the modulated signal is not obvious, the enable signal can be valid and the switch module 123 works. When the amplitude of the differential signal is greater than the amplitude of the reference signal, the switch module 123 connects the differential signal input terminal Vi and the first pole of the regulating transistor M. The differential signal can be simultaneously output to the positive input terminal V+ or the negative input terminal V- of the amplification unit 150 through the adjustment transistor M and the first resistor R4, that is, after the adjustment transistor M and the first resistor R4 are connected in series, they are connected in parallel with the second resistor R5, and the equivalent impedance of the amplification factor adjustment unit 120 is the equivalent impedance of the adjustment transistor M connected in series with the first resistor R4 and then connected in parallel with the second resistor R5. The substrate potential of the adjustment transistor M is controlled by the control unit 110, so that the equivalent impedance of the adjustment transistor M can be controlled, and then the equivalent impedance of the amplification factor adjustment unit 120 can be adjusted. In the above process, when the amplitude of the differential signal is greater than the amplitude of the reference voltage, the pre-demodulation circuit adjusts the gain according to the amplitude of the differential signal, which can further distinguish the baseband signal from the carrier signal, increase the signal-to-noise ratio of the baseband signal, and improve the accuracy of signal transmission.

[0063] Continue to refer Figure 8The switch module 123 includes a comparator COM and a switch transistor SW; the first input terminal of the comparator COM and the first electrode of the switch transistor SW serve as the first input terminal of the switch module 123, the enable terminal of the comparator COM serves as the enable terminal EN of the switch module 123, the second input terminal of the comparator COM serves as the second input terminal of the switch module 123, the output terminal of the comparator COM is connected to the gate of the switch transistor SW, and the second electrode of the switch transistor SW serves as the output terminal of the switch module 123.

[0064] Specifically, when the amplification factor adjustment unit 120 includes the first amplification factor adjustment unit 121 and the second amplification factor adjustment unit 122, the switch module 123 may include a first switch module 1231 and a second switch module 1232, the first switch module 1231 includes a first comparator COM1 and a first switch transistor SW1, the second switch module 1232 includes a second comparator COM2 and a second switch transistor SW2, and the reference signal input terminal VREF includes a first reference signal input terminal VREFP and a second reference signal input terminal VREFN. When the first differential signal is greater than the second differential signal, the first input terminal of the first comparator COM1 is a positive terminal +, and is connected to the first differential signal input terminal Vip. The second input terminal of the first comparator COM1 is a negative terminal -, and is connected to the first reference signal input terminal VREFP. The first reference signal provided by the first reference signal input terminal VREFP is a positive voltage signal. When the first differential signal is greater than the first reference signal, the first comparator COM1 outputs a high-level comparison signal to control the first switch transistor SW1 to be turned on. At this time, the substrate potential of the first adjustment transistor NM1 can be adjusted by the first control unit 111, and then the equivalent impedance of the first adjustment transistor NM1 can be adjusted, so that the gain of the pre-demodulation circuit can be adjusted. The first input terminal of the second comparator COM2 is the negative terminal -, and is connected to the second differential signal input terminal Vin. The second input terminal of the second comparator COM2 is the positive terminal +, and is connected to the second reference signal input terminal VREFN. The second reference signal provided by the second reference signal input terminal VREFN is a negative voltage signal. When the second differential signal is less than the second reference signal, the second comparator COM2 outputs a high-level comparison signal to control the second switch transistor SW2 to be turned on. At this time, the substrate potential of the second adjustment transistor NM2 can be adjusted by the second control unit 112, and then the equivalent impedance of the second adjustment transistor NM2 can be adjusted, so that the gain of the pre-demodulation circuit can be adjusted. When the equivalent impedance of the first regulating transistor NM1 and the equivalent impedance of the second regulating transistor NM2 are equal, the relationship between the output signal and the differential signal is as follows:

[0065]

[0066] Wherein, r5 is the resistance value of the second resistor R5, and r4 is the resistance value of the first resistor R4.

[0067] Fig. 9 A schematic diagram of the structure of a control unit provided by an embodiment of the present invention. Fig. 9 As shown, the control unit 110 includes an amplifier F1, a third resistor R6 and a fourth resistor R7; the positive input terminal F+ of the amplifier F1 is connected to the differential signal input terminal Vi, the negative input terminal F- of the amplifier F1 is connected to the first end of the third resistor R6 and the first end of the fourth resistor R7, the second end of the third resistor R6 is grounded GND, and the second end of the fourth resistor R7 and the output end of the amplifier F1 are connected to the control end Vb of the amplification factor adjustment unit 120.

[0068] Specifically, the third resistor R6 and the fourth resistor R7 determine the amplification factor of the amplifier F1, so that the control signal output by the amplifier F1 is linearly related to the differential signal. When the differential signal provided by the differential signal input terminal Vi increases, the voltage of the control signal output by the differential signal through the amplifier F1 increases, so that the potential of the control terminal Vb of the amplification factor adjustment unit 120 increases, thereby increasing the gain of the pre-demodulation circuit. When the differential signal provided by the differential signal input terminal Vi decreases, the voltage of the control signal output by the differential signal through the amplifier F1 decreases, so that the potential of the control terminal Vb of the amplification factor adjustment unit 120 decreases, thereby reducing the gain of the pre-demodulation circuit. The gain nonlinearity of the pre-demodulation circuit is achieved.

[0069] Fig.10 FIG. 1 is a schematic diagram of another control unit provided by an embodiment of the present invention. Fig.10 As shown, the control unit 110 includes a voltage follower module 113 and a resistance adjustment module 114; the input end of the voltage follower module 113 and the first input end of the resistance adjustment module 114 are connected to the differential signal input end Vi, the output end of the voltage follower module 113 is connected to the control end of the resistance adjustment module 114, the second input end of the resistance adjustment module 114 is connected to the positive input end V+ or the negative input end V- of the amplification unit 150, and the output end of the resistance adjustment module 114 is connected to the control end Vb of the amplification factor adjustment unit 120; the voltage follower module 113 is used to adjust the equivalent impedance of the resistance adjustment module 114 according to the differential signal.

[0070] Specifically, Fig.10exemplarily shows that the input end of the voltage follower module 113 and the first input end of the resistance adjustment module 114 are connected to the first differential signal input end Vip, and the second input end of the resistance adjustment module 114 is connected to the positive input end V+ of the amplification unit 150. When the first differential signal is greater than the second differential signal, the first differential signal increases, and the control signal output by the voltage follower module 113 increases, so that the potential of the control end of the resistance adjustment module 114 increases. When the potential of the control end of the resistance adjustment module 114 increases, the equivalent impedance of the resistance adjustment module 114 decreases, and at the same time, the voltage output by the resistance adjustment module 114 increases, so that the potential of the control end Vb of the amplification factor adjustment unit 120 increases, and the equivalent impedance of the amplification factor adjustment unit 120 is reduced. At the same time, the resistance adjustment module 114 and the amplification factor adjustment unit 120 are equivalent to being connected in parallel. When the equivalent impedances of the resistance adjustment module 114 and the amplification factor adjustment unit 120 are both reduced, the degree of reduction of the equivalent impedance of the amplification factor adjustment unit 120 can be increased, thereby increasing the degree of nonlinear gain change of the pre-demodulation circuit, which is beneficial to further improve the accuracy of signal transmission.

[0071] Continue to refer Fig.10 The voltage follower module 113 includes a plurality of transistors connected in series in a diode manner, each transistor being equivalent to a diode, and dividing the differential signal; one end of the plurality of transistors connected in series is connected to the differential signal input terminal Vi, and the other end is grounded GND, and at the same time, one of the connection points of the plurality of transistors connected in series is used as the output end of the voltage follower module 113, and is connected to the control end of the resistance adjustment module 114. When the differential signal increases, the divided voltage of one of the connection points of the plurality of transistors connected in series increases, so that the potential of the control end of the resistance adjustment module 114 increases. Exemplarily, Fig.10 The example in the figure shows that the voltage follower module 113 includes three transistors connected in series, namely a first transistor NM3, a second transistor NM4 and a third transistor NM5. The connection point between the second transistor NM4 and the third transistor NM5 serves as the output terminal of the voltage follower module 113 and is connected to the control terminal of the resistance adjustment module 114. When the differential signal increases, the potential of the connection point between the second transistor NM4 and the third transistor NM5 increases, so that the potential of the control terminal of the resistance adjustment module 114 increases. The equivalent impedance of the resistance adjustment module 114 decreases, and at the same time, the voltage output by the resistance adjustment module 114 increases, so that the potential of the control terminal Vb of the amplification factor adjustment unit 120 increases, thereby reducing the equivalent impedance of the amplification factor adjustment unit 120. By way of example, in Fig.10In the embodiment, the resistance adjustment module 114 includes a fourth transistor NM6 and a fifth resistor R8, the gate of the fourth transistor NM6 serves as the control terminal of the resistance adjustment module 114, the first electrode of the fourth transistor NM6 is connected to the first differential signal input terminal Vip, the second electrode of the fourth transistor NM6 serves as the output terminal of the resistance adjustment module 114 and is connected to the control terminal Vb of the amplification factor adjustment unit 120, and is connected to the positive input terminal V+ of the amplification unit 150 through the fifth resistor R8. When the differential signal increases and the gate potential of the fourth transistor NM6 increases, the equivalent impedance of the fourth transistor NM6 decreases, the second electrode potential of the fourth transistor NM6 increases, the equivalent impedance of the control amplification factor adjustment unit 120 decreases, and the sum of the equivalent impedance of the fourth transistor NM6 and the resistance of the fifth resistor R8 decreases. This increases the degree of reduction of the equivalent impedance of the amplification factor adjustment unit 120 after being connected in parallel with the equivalent impedance of the resistance adjustment module 114, thereby increasing the degree of nonlinear gain change of the pre-demodulation circuit, which is conducive to further improving the accuracy of signal transmission.

[0072] It should be noted that Fig.10 exemplarily shows a schematic diagram of the structure of the first control unit when the first differential signal is greater than the second differential signal. In other embodiments, the pre-demodulation circuit also includes a second control unit for adjusting the equivalent impedance of the second amplification factor adjustment unit 122 between the second differential signal input terminal Vin and the negative input terminal V- of the amplification unit 150. At this time, the connection mode of the transistors in the voltage follower module 113 or the type of transistors can be adjusted so that the voltage follower module 113 can control the equivalent impedance of the resistance adjustment module 114 according to the second differential signal. The connection mode of the transistors in the resistance adjustment module 114 or the type of transistors can also be adjusted so that the resistance adjustment module 114 can adjust the equivalent impedance of the second amplification factor adjustment unit 122 according to the differential signal, which will not be repeated here.

[0073] The embodiment of the present invention also provides a signal receiving end. The signal receiving end includes an analog-to-digital conversion circuit, a demodulation circuit, and a pre-demodulation circuit provided by any embodiment of the present invention; the pre-demodulation circuit is connected to the analog-to-digital conversion circuit, and the analog-to-digital conversion circuit is connected to the demodulation circuit; the pre-demodulation circuit is used to gain the differential signal to form a pre-demodulation signal; the analog-to-digital conversion circuit is used to perform analog-to-digital conversion on the pre-demodulation signal to form a digital signal; the demodulation circuit is used to demodulate the digital signal. Since the signal receiving end includes the pre-demodulation circuit provided by any embodiment of the present invention, it has the same beneficial effects as the pre-demodulation circuit provided by any embodiment of the present invention, which will not be repeated here.

[0074] Note that the above are only preferred embodiments of the present invention and the technical principles used. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and that various obvious changes, readjustments and substitutions can be made by those skilled in the art without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in more detail through the above embodiments, the present invention is not limited to the above embodiments, and may include more other equivalent embodiments without departing from the concept of the present invention, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A pre-demodulation circuit, characterized in that: It includes at least one control unit, at least one amplification factor adjustment unit, a first impedance unit, a second impedance unit and an amplification unit; The input end of the amplification factor adjustment unit and the input end of the control unit are connected to the differential signal input end, the output end of each amplification factor adjustment unit is connected to the positive input end or the negative input end of the amplification unit, the output end of each control unit is connected to the control end of an amplification factor adjustment unit, and the control unit is used to control the equivalent impedance of the amplification factor adjustment unit according to the differential signal provided by the differential signal input end; the first impedance unit is connected between the negative input end and the output end of the amplification unit, the input end of the second impedance unit is used to input a DC voltage, and the output end of the second impedance unit is connected to the positive input end of the amplification unit.

2. The pre-demodulation circuit according to claim 1, characterized in that: The amplification factor adjustment unit includes an adjustment transistor; the first electrode of the adjustment transistor and the input end of the control unit are connected to the differential signal input end, the substrate of the adjustment transistor is connected to the output end of the control unit, and the second electrode of the adjustment transistor is connected to the positive input end or the negative input end of the amplification unit; the control unit is used to adjust the equivalent impedance of the adjustment transistor according to the differential signal.

3. The pre-demodulation circuit according to claim 2, characterized in that: The differential signal input terminal includes a first differential signal input terminal and a second differential signal input terminal; At least one of the amplification factor adjustment units includes a first amplification factor adjustment unit and a second amplification factor adjustment unit; at least one of the control units includes a first control unit and a second control unit; the first amplification factor adjustment unit includes a first adjustment transistor; the first electrode of the first adjustment transistor and the input end of the first control unit are connected to the first differential signal input end, the substrate of the first adjustment transistor is connected to the output end of the first control unit, and the second electrode of the first adjustment transistor is connected to the positive input end of the amplification unit; the first control unit is used to adjust the equivalent impedance of the first adjustment transistor according to the first differential signal; the second amplification factor adjustment unit includes a second adjustment transistor; the first electrode of the second adjustment transistor and the input end of the second control unit are connected to the second differential signal input end, the substrate of the second adjustment transistor is connected to the output end of the second control unit, and the second electrode of the second adjustment transistor is connected to the negative input end of the amplification unit; the second control unit is used to adjust the equivalent impedance of the second adjustment transistor according to the second differential signal.

4. The pre-demodulation circuit according to claim 3, characterized in that: The first regulating transistor and the second regulating transistor are regulating transistors of opposite types; the first electrode of the first regulating transistor and the first electrode of the second regulating transistor are both sources or drains, or the first regulating transistor and the second regulating transistor are regulating transistors of the same type; The first electrode of the first regulating transistor is a drain or a source, the first electrode of the second regulating transistor is a source or a drain; the gate of the regulating transistor is connected to the drain.

5. The pre-demodulation circuit according to claim 2, characterized in that: The amplification factor adjustment unit also includes a first resistor; the first resistor is connected in series between the second electrode of the adjustment transistor and the positive input terminal of the amplification unit, or between the second electrode of the adjustment transistor and the negative input terminal of the amplification unit.

6. The pre-demodulation circuit according to claim 2, characterized in that: The amplification factor adjustment unit also includes a switch module and a second resistor, the first input end of the switch module and the first end of the second resistor are connected to the differential signal input end, the second input end of the switch module is connected to the reference signal input end, the enable end of the switch module is connected to the enable signal input end, the output end of the switch module is connected to the first electrode of the adjustment transistor, the second electrode of the adjustment transistor and the second end of the second resistor are connected to the positive input end or the negative input end of the amplification unit; the switch module is used to connect the differential signal input end and the first electrode of the adjustment transistor when the enable signal provided at the enable signal input end is valid and the differential signal and the parameter signal provided at the reference signal input end meet a preset condition.

7. The pre-demodulation circuit according to claim 6, characterized in that: The switch module includes a comparator and a switch transistor; The first input terminal of the comparator and the first electrode of the switching transistor serve as the first input terminal of the switching module, the enable terminal of the comparator serves as the enable terminal of the switching module, the second input terminal of the comparator serves as the second input terminal of the switching module, the output terminal of the comparator is connected to the gate of the switching transistor, and the second electrode of the switching transistor serves as the output terminal of the switching module.

8. The pre-demodulation circuit according to claim 1, characterized in that: The control unit includes an amplifier, a third resistor and a fourth resistor; The positive input terminal of the amplifier is connected to the differential signal input terminal, the negative input terminal of the amplifier is connected to the first end of the third resistor and the first end of the fourth resistor, the second end of the third resistor is grounded, and the second end of the fourth resistor and the output terminal of the amplifier are connected to the control terminal of the amplification factor adjustment unit.

9. The pre-demodulation circuit according to claim 1, characterized in that: The control unit includes a voltage following module and a resistance adjusting module; The input end of the voltage follower module and the first input end of the resistance adjustment module are connected to the differential signal input end, the output end of the voltage follower module is connected to the control end of the resistance adjustment module, the second input end of the resistance adjustment module is connected to the positive input end or the negative input end of the amplification unit, and the output end of the resistance adjustment module is connected to the control end of the amplification factor adjustment unit; the voltage follower module is used to adjust the equivalent impedance of the resistance adjustment module according to the differential signal.

10. A signal receiving end, characterized in that: It comprises an analog-to-digital conversion circuit, a demodulation circuit and a pre-demodulation circuit as described in any one of claims 1 to 9; the pre-demodulation circuit is connected to the analog-to-digital conversion circuit, and the analog-to-digital conversion circuit is connected to the demodulation circuit; the pre-demodulation circuit is used to gain a differential signal to form a pre-demodulation signal; the analog-to-digital conversion circuit is used to perform analog-to-digital conversion on the pre-demodulation signal to form a digital signal; and the demodulation circuit is used to demodulate the digital signal.

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