CN112436807A - Modulation broadband converter front-end integrated circuit based on secondary mixing technology - Google Patents

Modulation broadband converter front-end integrated circuit based on secondary mixing technology Download PDF

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CN112436807A
CN112436807A CN202011151417.XA CN202011151417A CN112436807A CN 112436807 A CN112436807 A CN 112436807A CN 202011151417 A CN202011151417 A CN 202011151417A CN 112436807 A CN112436807 A CN 112436807A
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CN112436807B (en
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刘素娟
何佳乐
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Beijing University of Technology
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    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03D—DEMODULATION OR TRANSFERENCE OF MODULATION FROM ONE CARRIER TO ANOTHER
    • H03D7/00—Transference of modulation from one carrier to another, e.g. frequency-changing
    • H03D7/16—Multiple-frequency-changing
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
    • Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

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Abstract

The invention provides a modulation broadband converter analog front-end circuit based on a secondary frequency mixing technology. According to the invention, a first-stage pre-modulation mixing stage is added in front of a multi-channel parallel modulation conversion circuit, a pseudo-random sequence with a hopping frequency of 1GHz is used in advance by the structure to mix with a sparse analog input signal with a maximum frequency of 500MHz, so that the Nyquist frequency requirement is met, the input signal is expanded to a full spectrum in advance, then the frequency of the pseudo-random sequence in each channel can be reduced to be half of the Nyquist frequency, namely 500MHz, and original information is not lost, so that the power consumption of the mixing part of the MWC front-end circuit is reduced under the condition of not influencing the rear-end reconstruction effect. Compared with the common MWC structure, the MWC structure has the advantages that the hardware circuit implementation difficulty and the system power consumption are reduced.

Description

Modulation broadband converter front-end integrated circuit based on secondary mixing technology
Technical Field
The invention relates to a front-end integrated circuit structure of a modulation broadband converter based on a compressed sensing theory and a secondary mixing technology, and belongs to the technical field of analog signal processing.
Background
The Shannon-Nyquist sampling theorem states that the sampling frequency in analog-to-digital conversion is at least twice the highest frequency of the input signal. With the development of communication technology, signal bandwidth is expanded, frequency of input signals is increased, higher requirements are put on signal processing capability of an Analog-to-digital conversion system, and great challenges are brought to an Analog-to-digital Converter (ADC), so that it is desirable to sample a broadband signal at a sampling rate far lower than the Nyquist frequency and still retain all information of the original signal. The compression perception theory is provided to achieve the aim, and the theory shows that when signals are sparse, combination of signal compression and sampling can be achieved through a global observation mode, all information of the signals can be obtained only through a small number of non-self-adaptive linear observation values, and therefore the sampling rate can be far lower than the Nyquist sampling rate. An Analog to Information Converter (AIC) structure is successfully established according to the theory, the structure firstly modulates an original signal, then performs low-pass filtering processing on the modulated signal, filters out a high-frequency part, reserves a low-frequency part, and finally uses a low-speed ADC for sampling and reconstructs the signal through a recovery algorithm.
In this context, various AIC structures such as random demodulation structures, random Modulation pre-integration and Modulation Wideband Converters (MWC) and so on are proposed in succession by the academia. The Eldar group of israeli university proposes a modulated wideband converter that processes input signals at multiple unknown frequency bands. The system structure mixes a periodic pseudorandom sequence with an input signal, spreads the signal to the whole frequency spectrum, then filters the mixed signal through a low-pass filter, and finally samples a low-speed ADC and reconstructs the signal by using a recovery algorithm. The structure has a good recovery effect on the multiband sparse signals, remarkably relieves the pressure on ADC sampling rate requirements when processing broadband signals, avoids the limitation of Nyquist theorem, and can save 2-10 times of system power consumption compared with the traditional signal processing method under the condition of low amplification gain.
Disclosure of Invention
The invention provides a modulation broadband converter analog front end integrated circuit based on a secondary mixing technology, which is characterized in that a primary premodulation mixing circuit is added in front of a multichannel parallel modulation conversion circuit, a pseudo-random sequence meeting Nyquist frequency requirements is mixed with an input signal in advance by using the structure, the input signal is expanded to a full spectrum in advance, all information of an original signal is output and reserved, then the frequency of the pseudo-random sequence in each channel can be greatly reduced without losing the original information, and power consumption generated by an MWC front end circuit is mainly concentrated on a mixing part, so that the realization difficulty of a hardware circuit and the system power consumption are reduced compared with a common MWC structure.
In order to achieve the purpose, the invention adopts the following technical scheme:
a modulation broadband converter analog front end integrated circuit based on a secondary mixing technology comprises a multichannel parallel modulation broadband conversion front end circuit consisting of a transconductance gain stage, a periodic pseudo-random sequence generator, a mixer and a low-pass filter. The overall circuit can be divided into four parts: a transconductance gain stage, a pre-mixing frequency stage, a secondary mixing frequency stage and a low-pass filter.
The circuit integrally adopts a fully differential structure, so that common-mode noise is effectively inhibited, and the reconstruction of a rear-end signal is more accurate.
A transconductance gain stage:
the transconductance gain stage circuit adopts a common source amplifier differential structure with a diode connected with a PMOS as a load, the circuit structure consists of 2 PMOS tubes and 2 NMOS tubes, source electrodes and substrates of the 2 PMOS tubes are connected with a power supply voltage VDD, grid electrodes are connected with respective drain electrodes, the drain electrodes are respectively connected with drain electrodes of the 2 NMOS tubes, grid electrodes of the 2 NMOS tubes are respectively connected with positive and negative phase input signals x (t), the source electrodes and the substrates of the NMOS tubes are grounded, the drain electrodes of the NMOS tubes with the grid electrodes connected with the positive phase input lead out a positive phase output, and the drain electrodes of the NMOS tubes with the grid electrodes connected with the negative phase input lead out a negative phase output. After the original multiband input signal x (t) is amplified by the transconductance gain stage, the signal voltage is converted into a signal current and is transmitted to the mixer.
Pre-mixing frequency stage:
an input signal x (t) enters a pre-mixing frequency stage after being amplified by a transconductance gain stage, wherein the pre-mixing frequency stage is composed of a mixer and a pseudo-random sequence generator. The pseudo-random sequence generator outputs a random sequence P (t) with equal probability change in one period, random transformation frequency of the random sequence +/-1 needs to be larger than or equal to Nyquist frequency of an input signal, the random sequence and the amplified input signal are subjected to first frequency mixing in a frequency mixer, a signal x (t) in the frequency mixer is multiplied by the random sequence P (t), in a frequency domain, convolution operation is performed on a signal spectrum corresponding to a random sequence spectrum, the signal x (t) spectrum changes the spectrum of the random sequence, the spectrum characteristic of the signal x (t) is carried on the whole frequency band of the random sequence, and the input signal is spread to the whole spectrum after frequency mixing.
The pseudo-random sequence generator is realized by adopting a 10-bit maximum length linear feedback shift register, and the main part comprises 10D triggers, 1 exclusive-OR gate and 2 inverters. The circuit is formed by cascading 10 identical D triggers, wherein each trigger comprises 5 ports which are respectively a reset signal control port, a set signal control port, a clock signal control port, a D end input and a Q end output. Pins are arranged at the Q output end of the 4 th trigger and the Q output end of the 10 th trigger and are connected to the input end of the exclusive-OR gate, the output end of the exclusive-OR gate is connected with a phase inverter and then is output to the D end of the first D trigger, so that a pseudo-random sequence with the output voltage jump value of 0 or 1.8V can be generated at the Q output end of the last D trigger, the output can directly drive the frequency mixer, and the pseudo-random sequence enables the positive phase and the negative phase of an output signal to pass through the frequency mixer through high-level and low-level switching. And the conversion frequency of the pseudo-random sequence directly determines the range of the bandwidth of a processable signal, in order to reduce the rise and fall time of the pseudo-random sequence and achieve better modulation effect, an inverter structure is added at the output end of the pseudo-random sequence generator to generate an inverted pseudo-random sequence, burrs appearing on the output waveform without the inverter are reduced, the amplitude range of the burrs is reduced from 50-100mV to 10-30mV, namely the modulation precision is obviously improved, and the driving capability of the pseudo-random sequence generator is increased.
Preferably, the mixer structure employs a passive mixer circuit. The passive mixer is a mixer with high hardware efficiency and simple design, and is suitable for MWC systems. The circuit is formed by a group of differential pairs by using 4 NMOS tubes as switches, positive phase signals amplified by a transconductance gain stage are connected to source electrodes of 2 NMOS tubes, grid electrodes of the 2 NMOS tubes are respectively controlled by positive and negative phase pseudorandom sequences, reverse phase signals are connected to source electrodes of the other 2 NMOS tubes, and the grid electrodes are also respectively controlled by the positive and negative phase pseudorandom sequences; the substrates of the 4 NMOS tubes are all grounded, the drain electrodes of the NMOS tubes with the grid electrodes and the source electrodes input in the same positive phase or in the same reverse phase lead out positive phase output, and the drain electrodes of the NMOS tubes with the grid electrodes and the source electrodes input in different phases lead out reverse phase output. When the positive phase pseudorandom sequence jumps to 1.8V, the reverse phase pseudorandom sequence jumps to 0V, the positive phase input signal keeps positive phase output, and the reverse phase input signal keeps reverse phase output; and conversely, when the positive phase pseudo random sequence jumps to 0V, the negative phase pseudo random sequence jumps to 1.8V, the positive phase input signal is converted into the negative phase output, and the negative phase input signal is converted into the positive phase output. Thus, the original signal is multiplied by ± 1. And when the signal is mixed with the pseudo-random sequence, the amplitude of the high level of the pseudo-random sequence is equal to 1.8V of the power supply voltage and is much larger than the amplitude of the signal (mV level), so that the passive mixer can have very high linearity.
A secondary mixer circuit:
the signals are pre-mixed and then transmitted to each sub-channel, and a secondary mixing circuit in each sub-channel consists of a mixer and a pseudo-random sequence generator, and adopts the same structures of the mixer and the pseudo-random sequence generator as those in the pre-mixing circuit. The difference is that the pseudo-random sequence conversion frequency adopted by each sub-channel in the secondary mixing circuit is far lower than the Nyquist frequency, so that the mixing of a plurality of channels can be avoided from occurring on the Nyquist frequency, the power consumption generated by the pseudo-random sequence generator and the mixing circuit is reduced, and the hardware implementation difficulty of the pseudo-random sequence generator and the mixing circuit is also reduced.
A low-pass filter:
preferably, the filter structure adopts a tunable biquadratic Gm-c low-pass filter. The circuit comprises 4 identical transconductance gain units gm1～4Cascade formation of each gmThere are 2 positive and negative input ports and 2 positive and negative output ports. The positive and negative phase output signals after the secondary frequency mixing are accessed to gm1Positive and negative phase input terminals of gm1Is connected with the inverting output terminal gm2Inverting input terminal of gm1Is connected with the positive phase output end gm2A positive phase input terminal of; gm2Is connected with the positive phase output end gm3Inverting input terminal of gm2Is connected with the inverting output terminal gm3A positive phase input terminal of; gm3Is connected with the positive phase output end gm4Positive phase input terminal of gm3Is connected with the inverting output terminal gm4The inverting input terminal of (1); gm4Is connected to gm1Is output in reverse phaseEnd sum gm2Positive phase output terminal of gm4Is connected to gm1Positive phase output terminal of (1) and (g)m2The inverting output terminal of (1); in gm2And gm3An adjustable capacitor C is added between the positive and negative output ports of each1,C2And is in gm3The positive and negative output ports are provided with an output pin of the whole circuit. The performance of the Gm-c filter is determined by the ratio of transconductance to capacitance, and the performance is more stable compared with the traditional RC filter of which the transfer function is determined by resistance capacitance. Gain unit g is increased due to transconductancemWhen the frequency converter is operated in an open loop state, the frequency use range is only determined by the gain bandwidth product, so that very high frequency can be achieved. The transconductance is determined by the size of the transconductance gain unit device, and the capacitance value can be adjusted by the designed adjustable structure, so that the performance of the filter can be adjusted by the logic control unit. The whole filter integrated circuit is realized by cascading a plurality of Nauta transconductance gain units, and the stability of a fully differential structure is ensured by adding a common-mode feedback circuit. An adjustable capacitor structure is added between the transconductance gain units and is realized by controlling a switch capacitor array by a logic gate. Compared with an ideal low-pass filter, a practical low-pass filter cannot completely pass a signal when intercepting a low-frequency signal, that is, the signal is accompanied by a certain attenuation. The amplitude-frequency characteristic shows that the ideal filter has sudden change at a cut-off frequency, the amplitude-frequency characteristic in a pass band is constant and zero in a stop band, the actual filter has gradual change transition at the cut-off frequency, the pass band has ripples, and the amplitude-frequency characteristic in the stop band gradually tends to zero. The low-pass filter circuit adopted in the invention is added with an adjustable capacitor structure, and the capacitance value is adjusted through the logic control unit, so that the compensation of the non-ideal frequency amplitude characteristic of the actual low-pass filter is achieved. The signal after twice frequency mixing intercepts the low frequency part through the filter, filters the high frequency part, and finally samples the signal through the low-speed analog-to-digital converter and recovers the original signal at the rear end.
The invention is characterized in that in the circuit structure of the modulation broadband converter, the whole structure is divided into four parts, and multiband original input signals are firstly amplified through a transconductance gain stage circuit; then mixing the frequency with a pseudo-random sequence with the switching frequency greater than or equal to the Nyquist frequency for the first time in a pre-mixing frequency stage; then the signals are transmitted to each channel for second frequency mixing, a mixer and a pseudo-random sequence generator adopted in the second frequency mixing have the same structure as those in the pre-mixing frequency circuit, but the conversion frequency of the pseudo-random sequence for frequency mixing with each channel signal can be far lower than the Nyquist frequency. (e.g., less than 50% below the Nyquist frequency) greatly reduces overall circuit power consumption as compared to conventional architectures that require each channel to have a pseudorandom sequence switching frequency greater than or equal to the Nyquist frequency; and finally, intercepting a low-frequency part of the signal subjected to secondary frequency mixing by a low-pass filter, and filtering a high-frequency part. The low-pass filter in the channel adopts a novel adjustable biquadratic Gm-c low-pass filter, an adjustable capacitor array is added between transconductance gain stage units, and a logic control unit is used for adjusting the capacitance so as to directly compensate the performance influence caused by parameter deviation of the actual low-pass filter.
Compared with the prior art, the invention has the following advantages:
compared with the traditional modulation broadband converter circuit, the invention adds the primary pre-mixing, performs pre-mixing with the pseudo-random sequence meeting the Nyquist frequency before the signal enters each sub-channel, and then transmits the signal to each channel for second mixing and filtering, and can adopt the pseudo-random sequence far lower than the Nyquist frequency when performing the second mixing in each channel, thereby greatly reducing the power consumption of the circuit and reducing the hardware realization difficulty of the pseudo-random sequence generator and the mixing circuit. And signals are subjected to secondary frequency mixing in each subchannel and then are sent into the adjustable Gm-C low-pass filter, and the designed novel adjustable Gm-C filter directly compensates the influence of parameter deviation on the performance of the filter in a capacitance value adjusting mode, so that the reconstruction precision is improved.
Drawings
FIG. 1 is a system block diagram of an embodiment of the present invention;
FIG. 2 is a block diagram of a transconductance gain stage according to an embodiment of the present invention;
FIG. 3 is a block diagram of a pseudo-random sequence generator according to an embodiment of the present invention;
FIG. 4 is a schematic diagram of a mixer circuit according to an embodiment of the present invention;
FIG. 5 is a schematic diagram of a low pass filter circuit according to an embodiment of the present invention;
FIG. 6 is a schematic diagram of a transconductance gain cell of a low pass filter according to an embodiment of the invention;
FIG. 7 is a schematic diagram of a switched capacitor array of a low pass filter according to an embodiment of the present invention;
FIG. 8 is a schematic diagram of a switched capacitor logic control according to an embodiment of the present invention;
Detailed Description
The following describes embodiments of the present invention with reference to the drawings.
The schematic diagram of the front-end integrated circuit system of the premodulation modulation broadband converter is shown in fig. 1. The whole circuit is designed by adopting an SMIC180nm CMOS process, and common mode noise is suppressed in a fully differential structure. A quadratic mixing 4-channel circuit structure is adopted.
As shown in fig. 2, the transconductance gain stage circuit adopts a common-source amplifier structure with a diode connected PMOS as a load, and appropriately increasing the gate length is helpful to reduce white noise and improve the quality of a reconstructed signal. The signal input bandwidth of MWC systems is directly determined by the-3 dB bandwidth of the transconductance stage, which requires the amplifier tube to be of large size and consume large power consumption in design. The size of the amplifier device adopted in the embodiment is 168um/0.5um, in simulation, the load is output by a 200fF capacitor, the-3 dB bandwidth of the transconductance gain stage circuit exceeds 1GHz, the phase margin is 76.09 degrees, and the power consumption is 6.26mW
The pre-mixing frequency stage circuit comprises: pseudo-random sequence generator, mixer.
As shown in FIG. 3, the pseudo-random sequence generator is composed of D flip-flops (DFF #1 ~ 10), exclusive OR gates (XOR), and inverters. The pseudo-random sequence generated by the shift register formed by the D trigger has the advantages of strong regularity, long period and the like. The voltage jump range of the pseudo-random sequence PN is 0, 1.8V, the output directly drives the mixer, and the forward and reverse of the output signal are modulated by the mixer through high and low level switching, so that the effect of multiplying the original signal by +/-1 is realized. In order to reduce the rising and falling time of the pseudo-random sequence and achieve better modulation effect, an inverter structure is added at the output end of the pseudo-random sequence generator, so that burrs appearing on the output waveform of the original inverter are reduced, the amplitude of the burrs is reduced to 10-30mV from 50-100mV, namely the modulation precision is remarkably improved, and meanwhile, the driving capability of the pseudo-random sequence generator is increased.
As shown in fig. 4, the mixer circuit adopts a passive mixer structure suitable for CMOS process, and has a simple design. The whole MOSFET functions as a switch, PN and
Figure BDA0002741425640000061
the port is connected with the output end of the pseudo-random sequence generator. PN sum of pseudo-random sequence generator
Figure BDA0002741425640000062
The output end generates a periodic pseudorandom sequence P (t) epsilon {0, 1} with the hopping frequency of 1 GHz. The pseudo-random sequence p (t) and the sparse analog multiband input signal x (t) amplified by the transconductance gain stage are down-converted in the mixer, and since the pseudo-random sequence has full spectrum and the hopping frequency is set to 1GHz to satisfy the Nyquist frequency, the pre-modulated signal z (t) contains all the information of the input signal.
The secondary mixing circuit comprises 4 paths of same pseudo-random sequence generators, mixers and low-pass filters.
Wherein the pseudo-random sequence generator and the mixer adopt the structures in fig. 3 and fig. 4. Except that the pseudo-random sequence generators in the 4 channels are in the PN sum
Figure BDA0002741425640000063
The output end generates a periodic pseudo-random sequence P with the frequency of 500MHz and different phase shiftsc(t) ∈ {0, 1}, c ═ 1, 2, 3, 4, and are mixed with the pre-mixed signal z (t), respectively. And then fed into the filter.
As shown in fig. 5, the low-pass filters are all novel adjustable Gm-C low-pass filters. With 4 transconductance gain stage units gm1～4Cascade, in which two adjustable capacitor arrays C are added1,C2The logic control unit is used for adjusting the capacitance so as to directly compensate the performance influence caused by the parameter deviation of the filter, and a common mode is addedThe feedback circuit ensures the stability of the fully differential circuit.
The transconductance gain unit is realized by a Nauta transconductance gain circuit, and has a higher bandwidth gain product, so that the filter has a higher cut-off frequency. As shown in fig. 6, the whole circuit is composed of 6 inverters Inv 1-6, Inv1 and Inv2 constitute the differential input of the circuit, Inv3 and Inv6 form a common-mode feedback circuit, and cross-coupled Inv4 and Inv5 are negative feedback. When the transconductance of Inv3, Inv4, Inv5 and Inv6 are consistent, the differential impedance load is very large, that is, in the pseudo-differential structure, the behaviors of the inverters are split and do not affect each other, so that the circuit in the form of the pseudo-differential circuit needs to be driven in a differential mode. And only one input node and one output node exist in the circuit, so that the circuit has good high-frequency characteristics. The transconductance gain unit circuit adopted in the embodiment is powered by a 1.8V power supply voltage, and under the condition of a load capacitor of 1pF, the simulation direct current gain is 22.21dB, the bandwidth gain product is 540.2MHz, and the phase margin is 94.13 degrees.
Fig. 7 is a switched capacitor array used in specific implementation, the capacitor switch control is realized by MOS transistors, in the figure, gatetrl 1-8 are gate end control signals of the MOS transistors, and ports of cappins 1-2 are connected with adjustable capacitors of biquad filters. Thus, the capacitance value of the access circuit can be directly adjusted only by proper logic control signals. When the grid electrode of the switching MOS tube is at a high level, the MOS tube works in a deep linear region, and the function of the MOS tube is equivalent to that of a linear resistor; when the grid electrode of the switching MOS tube is at a low level, the conduction channel of the MOS tube is turned off. In view of the fact that the width-to-length ratio of the MOS transistor is improved in design, and the size of the gate length is reduced to be beneficial to reducing the on-resistance, the size of the switching MOS transistor adopted in the embodiment is 40u/180 n.
FIG. 8 is a switched capacitor logic control module for controlling C coupled into a filter circuit1,C2The adjustable capacitor is set as an 8bit binary capacitor array. Wherein C is1The capacitance was set to 939.92fF-1.762357pF adjustable, step size 117.491 pF. C2The capacitance is set to 3.8975pF-4.934624pF adjustable, step 234.982 pF. In order to ensure layout matching, unit capacitors are 11um × 11um MIM capacitors with capacitance values of 117.491 fF. Implementing switched capacitor logicThe truth table of the control is shown in table 1.
Figure BDA0002741425640000071
Figure BDA0002741425640000081
Table 1 switched capacitor logic control truth table.

Claims (4)

1. A modulation broadband converter front end integrated circuit based on secondary mixing technology is characterized in that: the whole circuit is divided into four parts: a transconductance gain stage, a pre-mixing frequency stage, a secondary mixing frequency stage and a low-pass filter;
a transconductance gain stage:
the transconductance gain stage circuit adopts a common source amplifier differential structure with a diode connected with a PMOS as a load, the circuit structure consists of 2 PMOS tubes and 2 NMOS tubes, the source electrodes and substrates of the 2 PMOS tubes are connected with a power supply voltage VDD, the grid electrodes are connected with respective drain electrodes, the drain electrodes are respectively connected with the drain electrodes of the 2 NMOS tubes, the grid electrodes of the 2 NMOS tubes are respectively connected with positive and negative phase input signals x (t), the source electrodes and the substrates of the NMOS tubes are grounded, the drain electrodes of the NMOS tubes with the grid electrodes connected with the positive phase input lead out the positive phase output, and the drain electrodes of the NMOS tubes with the grid electrodes connected with the negative phase input lead out the negative phase; after an original multiband input signal x (t) is amplified by a transconductance gain stage, signal voltage is converted into signal current and the signal current is transmitted to a mixer;
pre-mixing frequency stage:
an input signal x (t) enters a pre-mixing frequency stage after being amplified by a transconductance gain stage, wherein the pre-mixing frequency stage is composed of a mixer and a pseudorandom sequence generator; the method comprises the steps that a pseudorandom sequence generator outputs a random sequence P (t) with equal probability change in one period, random conversion frequency of the random sequence +/-1 needs to be larger than or equal to Nyquist frequency of an input signal, the random sequence and the amplified input signal are subjected to first frequency mixing in a frequency mixer, a signal x (t) in the frequency mixer is multiplied by the random sequence P (t), in a frequency domain, convolution operation is performed on a signal spectrum corresponding to a random sequence spectrum, the signal x (t) spectrum changes the spectrum of the random sequence, the spectrum characteristic of the signal x (t) is carried on the whole frequency band of the random sequence, and the input signal is spread to the whole spectrum after frequency mixing;
a secondary mixer circuit:
the signals are pre-mixed and then transmitted to each sub-channel, a secondary mixing circuit in each sub-channel consists of a mixer and a pseudo-random sequence generator, and the structures of the mixer and the pseudo-random sequence generator are the same as those in the pre-mixing circuit; the pseudo-random sequence switching frequency adopted by each sub-channel in the secondary mixing circuit is lower than the Nyquist frequency.
2. The modulated wideband converter front end integrated circuit based on quadratic mixing technology of claim 1, characterized in that:
a low-pass filter: the structure adopts an adjustable biquadratic Gm-c low-pass filter; the circuit comprises 4 identical transconductance gain units gm1～4Cascade formation of each gm2 positive and negative input ports and 2 positive and negative output ports are arranged; the positive and negative phase output signals after the secondary frequency mixing are accessed to gm1Positive and negative phase input terminals of gm1Is connected with the inverting output terminal gm2Inverting input terminal of gm1Is connected with the positive phase output end gm2A positive phase input terminal of; gm2Is connected with the positive phase output end gm3Inverting input terminal of gm2Is connected with the inverting output terminal gm3A positive phase input terminal of; gm3Is connected with the positive phase output end gm4Positive phase input terminal of gm3Is connected with the inverting output terminal gm4The inverting input terminal of (1); gm4Is connected to gm1And g is the inverting output ofm2Positive phase output terminal of gm4Is connected to gm1Positive phase output terminal of (1) and (g)m2The inverting output terminal of (1); in gm2And gm3An adjustable capacitor C is added between the positive and negative output ports of each1,C2And is in gm3The positive and negative output ports are provided with an output pin of the whole circuit.
The filter integrated circuit is integrally realized by cascading a plurality of Nauta transconductance gain units, and a common-mode feedback circuit is added to ensure the stability of a fully differential structure; an adjustable capacitor structure is added between the transconductance gain units and is realized by controlling a switch capacitor array by a logic gate; the original signal is sampled by a low-speed analog-to-digital converter and recovered at the back end.
3. The modulated wideband converter front end integrated circuit based on quadratic mixing technology of claim 1, characterized in that:
the pseudo-random sequence generator is realized by adopting a 10-bit maximum length linear feedback shift register and comprises 10D triggers, 1 exclusive-OR gate and 2 inverters; the circuit is formed by cascading 10 identical D triggers, wherein each trigger comprises 5 ports which are respectively a reset signal control port, a set signal control port, a clock signal control port, a D end input and a Q end output; pins are arranged at the Q output end of the 4 th trigger and the Q output end of the 10 th trigger and are connected to the input end of an exclusive-OR gate, the output end of the exclusive-OR gate is connected with a phase inverter and then is output to the D end of the first D trigger, so that a pseudo-random sequence with the output voltage jump value of 0 or 1.8V can be generated at the Q output end of the last D trigger, and the pseudo-random sequence enables the positive phase and the negative phase of an output signal to pass through a frequency mixer through high level and low level switching; and the conversion frequency of the pseudo-random sequence directly determines the range of the bandwidth of a processable signal at the output end of the pseudo-random sequence generator and then adds an inverter structure to generate an inverted pseudo-random sequence, so that the burrs generated on the output waveform without adding the inverter originally are reduced, and the amplitude range of the burrs is reduced from 50-100mV to 10-30 mV.
4. The modulated wideband converter front end integrated circuit based on quadratic mixing technology of claim 1, characterized in that:
the mixer structure adopts a passive mixer circuit; the non-circuit uses 4 NMOS tubes as switches to form a group of differential pairs, positive phase signals amplified by a transconductance gain stage are connected to the source electrodes of 2 NMOS tubes, the grid electrodes of the 2 NMOS tubes are respectively controlled by positive and negative phase pseudorandom sequences, reverse phase signals are connected to the source electrodes of the other 2 NMOS tubes, and the grid electrodes are also respectively controlled by the positive and negative phase pseudorandom sequences; the substrates of the 4 NMOS tubes are all grounded, the drain electrodes of the NMOS tubes with the grid electrodes and the source electrodes input in the same positive phase or in the same reverse phase lead out positive phase output, and the drain electrodes of the NMOS tubes with the grid electrodes and the source electrodes input in different phases lead out reverse phase output.
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CN110943954A (en) * 2019-11-28 2020-03-31 北京理工大学 Greedy algorithm based mixing sequence optimization method for modulation broadband converter

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CN106849876A (en) * 2017-02-09 2017-06-13 中国科学技术大学 A kind of use multiple feedback mutual conductance enhancing and the low-power consumption wide band radio-frequency frequency mixer of common-mode feedback active load
CN107979379A (en) * 2017-11-20 2018-05-01 北京工业大学 Modulation wide-band transducer AFE(analog front end) development board based on compressive sensing theory
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CN117639723A (en) * 2023-12-29 2024-03-01 西安航天民芯科技有限公司 Analog front-end attenuator circuit

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