A resonant sensor based on sideband excitation

Abstract

The present invention discloses a resonant sensor based on sideband excitation, comprising: a MEMS resonator and a feedback control system, wherein the resonator comprises at least two electrodes, and the feedback control system is used to realize feedback closed-loop control and adaptively adjust the frequency of the sideband excitation signal during the sensing process, thereby maintaining the self-excited oscillation of the resonator. The feedback control system comprises: a first feedback control circuit and a second feedback control circuit, wherein the first feedback control circuit is used to track the frequency change of the first-order mode of the resonator in real time by detecting the change of the phase difference, thereby demodulating the oscillation amplitude of the first-order mode of the resonator and generating a demodulation reference signal equal to the fundamental frequency of the oscillation; the second feedback control circuit is used to output the sideband excitation signal by detecting the change of the oscillation amplitude, and at the same time extract the frequency information of the sideband excitation signal as the sensor output. The present invention can solve the problems of low sensitivity and low resolution of the resonant acceleration sensor in the prior art.

Description

Technical Field

[0001] The present invention belongs to the field of micro-electromechanical systems and their sensing and control in the field of information engineering; more specifically, it relates to a feedback control circuit of a resonant MEMS sensor for sideband excitation modulation self-oscillation effect, so as to improve the sensitivity of the MEMS sensor. Background Art

[0002] MEMS sensors have advantages such as small size and low cost. They are used in commercial fields such as consumer electronics and automotive electronics, as well as high-end fields such as oil exploration and gravity survey. Compared with MEMS sensors that use voltage output, including capacitance readout and light intensity readout, MEMS resonant sensors use frequency output, which has the advantages of stability and high resolution. Therefore, it is the development direction and trend of high-performance MEMS sensors. In order to achieve high stability and resolution, it is necessary to improve the sensitivity of MEMS resonant sensors.

[0003] At present, the main methods for improving the sensitivity of MEMS resonant sensors are force, displacement, strain amplification, and the use of higher-order modes with higher sensitivity. The force and displacement amplification methods are more common, such as STMicroelectronics' patent US9354246B2, etc., and their amplification factors are limited by the size of the lever. For smaller sizes in MEMS sensors, the amplification factor of the lever is usually limited. The strain amplification method, such as Kose, et al. Journal of Micromechanics and Microengineering, 26 (4), 045012, 2016, etc., is limited by the device processing technology. The method of using high-order modes to improve sensitivity, such as Zhao, Chun, et al. Journal of Microelectromechanical Systems, 28 (3), pp. 324-326, 2019, is limited by the low signal-to-noise ratio of high-order modes. Even if the sensitivity is improved, the final sensor noise is not significantly improved. These limiting factors will reduce the efficiency of sensitivity improvement, so it is necessary to explore new ways to improve sensitivity and thus realize high-performance MEMS resonant sensors.

[0004] In recent years, the study of the sideband excitation effect of MEMS resonators has become one of the research hotspots. By applying a sideband excitation modulated AC voltage signal to the MEMS resonator, and the frequency of the signal is equal to the sum of multiple intrinsic mode frequencies of the MEMS resonator, and the amplitude of the signal meets certain conditions, the quality factor and vibration amplitude of the resonator will be greatly improved, and even enter a self-excited oscillation state. However, to date, sensors based on this effect have not yet been realized. Summary of the invention

[0005] In view of the defects of the prior art, the purpose of the present invention is to provide a resonant sensor based on sideband excitation, aiming to solve the problems of low sensitivity and low resolution of the sensor in the prior art due to the limited size of the resonator lever, the difficulty of device processing technology and the low signal-to-noise ratio of high-order modes.

[0006] The present invention provides a resonant sensor based on sideband excitation, comprising: a MEMS resonator and a feedback control system, wherein the MEMS resonator comprises at least two electrodes, a driving signal and a sideband excitation signal are applied through one of the electrodes, and the other electrode is used as a detection electrode; the feedback control system is connected to the MEMS resonator, and is used to realize feedback closed-loop control, and adaptively adjust the frequency of the sideband excitation signal during the sensing process, so as to maintain the self-excited oscillation of the MEMS resonator.

[0007] Furthermore, the feedback control system includes: a first feedback control circuit and a second feedback control circuit, the input end of the first feedback control circuit is connected to the detection end of the MEMS resonator, and is used to track the frequency change of the first-order mode of the MEMS resonator in real time by detecting the phase difference change, and extract the oscillation amplitude of the first-order mode; the input end of the second feedback control circuit is connected to the output end of the first feedback control circuit, and the output end of the second feedback control circuit is connected to the feedback control end of the MEMS resonator, and is used to output the sideband excitation signal by detecting the change of the oscillation amplitude.

[0008] Furthermore, the first feedback control circuit includes: a transimpedance amplifier circuit, an analog-to-digital conversion circuit and a digital phase-locked amplifier circuit connected in sequence, the input end of the transimpedance amplifier circuit serves as the input end of the first feedback control circuit, and the output end of the digital phase-locked amplifier circuit serves as the output end of the first feedback control circuit; the transimpedance amplifier circuit is used to convert the current generated by the movement of the MEMS resonator into a voltage signal; the analog-to-digital conversion circuit is used to convert the analog signal output by the transimpedance amplifier circuit into a digital signal; the digital phase-locked amplifier circuit is used to read out the oscillation amplitude of the first-order mode of the MEMS resonator and the phase difference between the first-order mode frequency signal of the MEMS resonator and a reference frequency signal, and to track the frequency change of the first-order mode of the MEMS resonator in real time by detecting the change in the phase difference.

[0009] The digital phase-locked amplifier circuit comprises: a multiplier, a digital low-pass filter, an amplitude phase demodulator, a first adder, a first PID controller, a second adder and a first digital controlled oscillator connected in sequence; the input end of the multiplier is connected to the output end of the analog-to-digital converter and the output end of the first digital controlled oscillator; the first input end of the first adder is connected to the output end Φ of the amplitude phase demodulator, and the second input end of the first adder is connected to the given initial phase shift Φ oThe first input end of the second adder is connected to the output end of the first PID controller, and the second input end of the second adder is connected to the given initial center frequency f o ; The multiplier is used to multiply the digital signal output by the analog-to-digital conversion circuit with a pair of orthogonal signals sin and cos output by the first digitally controlled oscillator; the digital low-pass filter is used to filter out the high-frequency signal output by the multiplier; the amplitude phase demodulator is used to demodulate the phase information Φ and amplitude information A of the first-order modal frequency signal of the MEMS resonator; the first PID controller controls the output frequency of the first digitally controlled oscillator by adjusting the phase information output by the amplitude phase demodulator; the first digitally controlled oscillator is adjusted by the PID controller to output a pair of orthogonal frequency signals sin and cos.

[0010] Furthermore, the second feedback control circuit includes: a control module and a feedback adjustment module connected in sequence; the input end of the control module serves as the input end of the second feedback control circuit, and the output end of the feedback adjustment module serves as the output end of the second feedback control circuit; the control module outputs a control signal for controlling the frequency of the sideband excitation signal by detecting the change in the oscillation amplitude of the first-order mode of the MEMS resonator; the feedback adjustment module is used to output the sideband excitation signal from the first output end according to the control signal, so that the sensor operates in a self-excited oscillation state; and at the same time, the frequency information of the sideband excitation signal is extracted and output from the second output end.

[0011] Wherein, the control module adopts a lookup table method, a PID regulation method, a linear fitting method or a polynomial fitting regulation method to control the frequency of the sideband excitation signal.

[0012] As an embodiment of the present invention, the control module includes: a third adder, a fourth adder and a second PID controller; the first input end of the third adder is used as the input end of the control module, and the second input end of the third adder is connected to a given initial amplitude offset A o signal, the input end of the second PID controller is connected to the output end of the third adder, the first input end of the fourth adder is connected to the output end of the second PID controller, and the second input end of the fourth adder is used to connect the given initial center frequency f oo signal, and the output end of the fourth adder serves as the output end of the control module.

[0013] Among them, the feedback regulation module includes: a second digitally controlled oscillator, a digital-to-analog conversion circuit, and an amplitude adjustment circuit connected in sequence; the input end of the second digitally controlled oscillator serves as the input end of the feedback regulation module, the second output end of the second digitally controlled oscillator serves as the second output end of the feedback regulation module, the second digitally controlled oscillator is used to output a sideband excitation signal as a feedback signal, and at the same time extract the frequency information of the sideband excitation signal as a sensing output; the input end of the digital-to-analog conversion circuit is connected to the first output end of the feedback regulation module, the digital-to-analog conversion circuit is used to convert the digital signal output by the second digitally controlled oscillator into an analog signal; the input end of the amplitude adjustment circuit is connected to the output end of the digital-to-analog conversion circuit, the output end of the amplitude adjustment circuit serves as the output end of the feedback regulation module, and the amplitude adjustment circuit is used to adjust the amplitude of the sideband excitation signal so that it meets the amplitude requirement of the self-excited oscillation of the MEMS resonator.

[0014] In the embodiment of the present invention, the MEMS resonator may be a resonator with two degrees of freedom and two electrodes, or a resonator with two degrees of freedom and four electrodes.

[0015] Among them, the frequency of the sideband excitation signal is equal to a*f p +b*f q , where f p and f q are the p-order and q-order modal eigenfrequencies respectively, p and q are mutually unequal positive integers; a and b are positive integers.

[0016] The above technical solution conceived by the present invention, compared with the prior art, uses the characteristics of the sideband excitation to maintain the self-oscillation of the MEMS resonator, and realizes adaptive adjustment of the frequency of the sideband excitation signal during the sensing process through a closed-loop feedback system, thereby maintaining the self-oscillation of the MEMS resonator, and finally improving the sensitivity of the resonant MEMS sensor by reading the frequency of the sideband excitation signal; the present invention has the following technical effects:

[0017] (1) In the present invention, the improvement of sensor sensitivity is not limited by the process. Any resonant sensor can achieve sensitivity improvement through this method by taking advantage of the higher sensitivity of high-order modes.

[0018] (2) While the present invention takes advantage of the higher sensitivity of the higher-order mode, it is not negatively affected by the problem of lower signal-to-noise ratio of the higher-order mode, because the first feedback control circuit still tracks the frequency signal of the first-order mode, and the amplitude is also the amplitude of the first-order mode. Since the sideband excitation is used to connect the first-order mode with the higher-order mode, the effect of sensitivity transfer is achieved, thereby improving the sensitivity. In addition, the first-order mode signal-to-noise ratio is relatively high, and after adding the sideband excitation, the quality factor and vibration amplitude of the resonator will be greatly improved, so the resolution can be effectively improved while improving the sensitivity.

[0019] (3) The implementation method of the present invention is simple and low-cost, and can be implemented using commercially available field programmable gate array circuits (FPGAs), microcontroller circuits, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a principle block diagram of a resonant-oriented sensor provided by an embodiment of the present invention;

[0021] Figure 2 is a schematic structural diagram of a MEMS resonator in a resonant-oriented sensor provided by a first embodiment of the present invention;

[0022] Figure 3 is a schematic structural diagram of a MEMS resonator in a resonance-oriented sensor provided in a second embodiment of the present invention;

[0023] Figure 4 It is a schematic diagram of the circuit structure of a resonant sensor provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0025] The present invention provides a new method for improving the sensitivity of a resonant MEMS sensor. The present invention utilizes sideband excitation to maintain the self-oscillation characteristic of a MEMS resonator, and realizes adaptive adjustment of the sideband excitation signal frequency during the sensing process by realizing a closed-loop feedback system, thereby maintaining the self-oscillation of the MEMS resonator, and finally improving the sensitivity of the MEMS resonant sensor by reading the sideband excitation signal frequency.

[0026] In the present invention, the MEMS resonant sensor includes a MEMS resonator and a feedback control system, wherein the MEMS resonator includes at least two electrodes, a driving signal and a sideband excitation signal are applied through one of the electrodes, and the other electrode is used as a detection electrode; the feedback control system is connected to the MEMS resonator to realize feedback closed-loop control and adaptively adjust the frequency of the sideband excitation signal during the sensing process, thereby maintaining the self-excited oscillation of the MEMS resonator.

[0027] In the embodiment of the present invention, the resonant frequency of the MEMS resonant sensor is a function of the physical quantity to be measured; the MEMS resonator has multiple eigenfrequencies, which are respectively denoted as f1, f2, ..., f n, where the subscript n (n is a positive integer) represents the nth order eigenmode. In addition, the resonator is also equipped with at least two electrodes, one of which can be used to apply a drive signal and a sideband excitation signal, and the other electrode is used to detect the motion displacement or speed of the resonator. It should be noted that there can be more than two electrodes. For example, when three electrodes are equipped, one is used to apply a drive signal, one is used to apply a sideband excitation signal, and one is used to detect the motion of the resonator. If four or more electrodes are equipped, one is used to apply a drive signal, one is used to apply a sideband excitation signal, and one is used to detect the motion of the resonator. The remaining electrodes can be used to apply a reference voltage signal, such as a 0V voltage signal, which can be used to isolate signal coupling crosstalk.

[0028] Figure 1 The principle block diagram of the resonance-oriented sensor provided by the embodiment of the present invention is shown; for the convenience of explanation, only the part related to the embodiment of the present invention is shown, which is described in detail as follows:

[0029] The resonant-oriented sensor includes: a MEMS resonator 1 and a feedback control system, and the feedback control system includes: a first feedback control circuit 2 and a second feedback control circuit 3, wherein the input end of the first feedback control circuit 2 is connected to the detection end of the MEMS resonator 1, and is used to track the frequency change of the first-order mode of the MEMS resonator 1 in real time by detecting the phase difference change, and demodulate the oscillation amplitude of the first-order mode of the MEMS resonator; the input end of the second feedback control circuit 3 is connected to the output end of the first feedback control circuit 2, and the output end of the second feedback control circuit 3 is connected to the feedback control end of the MEMS resonator 1, and is used to output a sideband excitation signal by detecting the change of the oscillation amplitude.

[0030] In an embodiment of the present invention, the first feedback control circuit 2 includes: a transimpedance amplifier circuit 21, an analog-to-digital conversion circuit 22 and a digital phase-locked amplifier circuit 23 connected in sequence, the input end of the transimpedance amplifier circuit 21 serves as the input end of the first feedback control circuit 2, and the output end of the digital phase-locked amplifier circuit 23 serves as the output end of the first feedback control circuit 2; the transimpedance amplifier circuit 21 is used to convert the current generated by the movement of the MEMS resonator 1 into a voltage signal; the analog-to-digital conversion circuit 22 is used to convert the analog signal output by the transimpedance amplifier circuit 21 into a digital signal; the digital phase-locked amplifier circuit 23 is used to read out the oscillation amplitude of the first-order mode of the MEMS resonator 1 and the phase difference between the first-order mode frequency signal of the MEMS resonator 1 and a reference frequency signal, and to track the frequency change of the first-order mode of the MEMS resonator in real time by detecting the change in the phase difference.

[0031] In an embodiment of the present invention, the second feedback control circuit 3 includes: a control module 31 and a feedback adjustment module 32 connected in sequence; the input end of the control module serves as the input end of the second feedback control circuit 3, and the output end of the feedback adjustment module 32 serves as the output end of the second feedback control circuit 3; the control module 31 outputs a control signal for controlling the frequency of the sideband excitation signal by detecting the change in the oscillation amplitude of the first-order mode of the MEMS resonator 1; the feedback adjustment module 32 is used to output the sideband excitation signal from the first output end according to the control signal, so that the sensor operates in a self-excited oscillation state; and at the same time, the frequency information of the sideband excitation signal is extracted and output from the second output end.

[0032] In the present invention, the digital phase-locked amplifier circuit is used to read out the oscillation amplitude of the first-order mode of the resonator, and the phase difference between the first-order mode frequency signal of the resonator and a reference frequency signal. By detecting the changes in the phase difference and the oscillation amplitude, a two-stage feedback system is formed. The first feedback control circuit 2 tracks the frequency change of the first-order mode of the resonator in real time by detecting the change in the phase difference, and demodulates the oscillation amplitude of the first-order mode of the MEMS resonator. After the first feedback control circuit 2 is stable, the second feedback control circuit 3 starts to work. The second feedback control circuit 3 includes a control module and a feedback adjustment module, which controls the output of the sideband excitation signal of the feedback element behind by detecting the change in the oscillation amplitude. The control module controls the frequency of the sideband excitation signal output by the feedback adjustment module by detecting the oscillation amplitude output by the resonator through a specific control algorithm; the feedback adjustment module is adjusted by the control module and is used to output the sideband excitation signal so that the sensor works in a self-excited oscillation state, and at the same time extracts the frequency information of the sideband excitation signal as the sensor output. The frequency of the sideband excitation signal should be equal to a*f p +b*f q , where f p and f q are p-order and q-order modal eigenfrequencies respectively, p and q are mutually unequal positive integers; a and b are positive integers, a and b can be equal. The pump signal is generated by the aforementioned feedback regulation module in the present invention, and the feedback regulation module is controlled by the control module.

[0033] Figure 2 The structure of the MEMS resonator in the resonant sensor provided by the first embodiment of the present invention is shown. For the convenience of explanation, only the part related to the first embodiment of the present invention is shown, which is described in detail as follows:

[0034] The first embodiment of the present invention provides a structure of a two-degree-of-freedom two-electrode resonant MEMS sensor based on active coupling, wherein the A1 electrode can be used to apply a driving signal and a sideband excitation signal; the A2 electrode can be used to detect the motion displacement or speed of the resonator; and the A3 electrode is used to apply a DC bias voltage.

[0035] The resonant MEMS accelerometer has multiple eigenfrequencies, which are denoted as f1, f2, ..., fn, respectively, where the subscript n (n is a positive integer) represents the nth order eigenmode. It mainly includes two electrodes, one of which can be used to apply a drive signal and a sideband excitation signal, and the other electrode is used to detect the motion displacement or velocity of the resonator. By applying a sideband excitation signal, the sensor can work in a self-excited oscillation state, and the frequency of the sideband excitation signal is equal to a*f p +b*f q , where f p and f q They are the p-order and q-order modal eigenfrequencies respectively, p and q are mutually unequal positive integers; a and b are positive integers, a and b can be equal; and their amplitudes should meet specific conditions (determined by the specific design of the device). The sideband excitation signal is generated by the feedback adjustment module in the present invention, and its frequency is controlled by the control module.

[0036] Compared with the prior art in which the sensor has low sensitivity and low resolution due to limited resonator lever size, difficult device processing technology, low high-order modal signal-to-noise ratio and other reasons, the present invention proposes a solution that can improve the sensitivity and resolution of the sensor.

[0037] Figure 3 : is a schematic diagram of the structure of a MEMS resonator in a resonant sensor provided by the second embodiment of the present invention. For the sake of convenience, only the part related to the second embodiment of the present invention is shown, which is described in detail as follows:

[0038] The second embodiment of the present invention provides a structure of a two-degree-of-freedom four-electrode resonant MEMS sensor based on active coupling, wherein the B1 electrode can be used to apply a driving signal; the B2 electrode can be used to apply a sideband excitation signal; the B3 electrode can be used to apply a 0V voltage signal; the B4 electrode can be used to detect the motion displacement or speed of the resonator; and the B5 electrode is used to apply a DC voltage.

[0039] Compared with the structure shown in the first embodiment, this structure has two more electrodes, and the electrodes can be allocated as follows: one is used to apply a drive signal, one is used to apply a sideband excitation signal, and one is used to detect the movement of the resonator. In addition, the remaining electrode can be used to apply a reference voltage signal, such as a 0V voltage signal, which can be used to isolate signal coupling crosstalk. Other parameter settings are the same as those of the structure shown in the first embodiment, and will not be repeated here.

[0040] Figure 4 The circuit structure of a resonant sensor provided by an embodiment of the present invention is shown. For the sake of convenience, only the part related to the embodiment of the present invention is shown, which is described in detail as follows:

[0041] A front-end transimpedance amplifier (TIA) circuit is used to convert the current generated by the resonator movement into a voltage signal;

[0042] An analog-to-digital conversion circuit (ADC), used for converting an analog voltage signal into a digital voltage signal to serve as an input signal of a digital phase-locked amplifier circuit;

[0043] The digital phase-locked amplifier circuit is used to read out the oscillation amplitude of the output signal of the resonant MEMS acceleration sensor, and the phase difference between the output signal of the sensor and a reference frequency signal, wherein the oscillation amplitude and the phase difference are respectively used as inputs of the two-stage feedback system. The first feedback control circuit 2 tracks the frequency change of the first-order mode of the resonator in real time by detecting the change of the phase difference. Before the first feedback control circuit 2 is stable, the system is not suitable for sensing. After the first feedback control circuit 2 is stable, the second feedback control circuit 3 starts to work, and the system can realize sensing at this time. The second-stage feedback control system controls the output sideband excitation signal of the subsequent feedback element by detecting the change of the oscillation amplitude.

[0044] As an embodiment of the present invention, the digital phase-locked amplifier circuit 23 includes: a multiplier, a digital low-pass filter, an amplitude phase demodulator, a first adder, a first PID controller, a second adder and a first digital controlled oscillator connected in sequence; the input end of the multiplier is connected to the output end of the analog-to-digital converter and the output end of the first digital controlled oscillator; the first input end of the first adder is connected to the output end Φ of the amplitude phase demodulator, and the second input end of the first adder is connected to the given initial phase shift Φ o The first input end of the second adder is connected to the output end of the first PID controller, and the second input end of the second adder is connected to the given initial center frequency f o ; The multiplier is used to multiply the digital signal output by the analog-to-digital conversion circuit 22 with a pair of orthogonal signals sin and cos output by the first digitally controlled oscillator; the digital low-pass filter is used to filter out the high-frequency signal output by the multiplier; the amplitude-phase demodulator is used to demodulate the phase information Φ and amplitude information A of the first-order modal frequency signal of the MEMS resonator; the first PID controller controls the output frequency of the first digitally controlled oscillator by adjusting the phase information output by the amplitude-phase demodulator; the first digitally controlled oscillator is adjusted by the PID controller to output a pair of orthogonal frequency signals sin and cos.

[0045] The control module controls the frequency of the sideband excitation signal output by the feedback adjustment module by detecting the oscillation amplitude output by the resonator, so that the frequency of the sideband excitation signal output by the feedback adjustment module is equal to a*f p +b*f q , where f p and f qThey are the p-order and q-order modal eigenfrequencies respectively, p and q are mutually unequal positive integers; a and b are positive integers, and a and b can be equal. When the input voltage of the control module (i.e., the oscillation amplitude of the MEMS resonator) changes, it means that the MEMS resonator senses the change in the input signal. The controller detects the magnitude of the amplitude change and adopts one or more adjustment methods. The specific adjustment methods include but are not limited to: lookup table (LUT) method, PID adjustment, linear fitting adjustment, polynomial fitting adjustment, etc., to generate a control signal accordingly, thereby controlling the frequency of the sideband excitation signal.

[0046] As an embodiment of the present invention, the control module 31 includes: a first adder, a second adder and a PID controller; the first input end of the first adder is used as the input end of the control module, and the second input end of the first adder is connected to the given initial amplitude offset A o signal, the input end of the PID controller is connected to the output end of the first adder, the first input end of the second adder is connected to the output end of the PID controller, and the second input end of the second adder is connected to the given initial center frequency f oo signal, and the output end of the second adder serves as the output end of the control module.

[0047] The feedback adjustment module outputs the corresponding sideband excitation signal as a feedback signal according to the control signal output by the control module, and extracts its frequency information as the system output. The module can be composed of a numerically controlled oscillator (NCO), a digital-to-analog conversion circuit (DAC), and an amplitude adjustment circuit (AMP). The NCO is used to output the sideband excitation signal as a feedback signal, and extract the frequency information of the sideband excitation signal as the system output; the DAC is used to convert the digital signal output by the NCO into an analog signal. The DAC can also be removed. If removed, the multi-bit frequency signal output by the NCO must be converted into a single-bit frequency signal, that is, a square wave signal; the AMP is used to adjust the amplitude of the sideband excitation signal to meet the sideband excitation signal amplitude requirements of the self-oscillation of the MEMS resonator.

[0048] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A resonant sensor based on sideband excitation, characterized in that: include: MEMS resonator (1) and feedback control system, The MEMS resonator (1) comprises at least two electrodes, a driving signal and a sideband excitation signal are applied through one of the electrodes, and the other electrode is used as a detection electrode; The feedback control system is connected to the MEMS resonator (1) to implement feedback closed-loop control and adaptively adjust the frequency of the sideband excitation signal during the sensing process, thereby maintaining the self-excited oscillation of the MEMS resonator; The feedback control system comprises: a first feedback control circuit (2) and a second feedback control circuit (3), The input end of the first feedback control circuit (2) is connected to the detection end of the MEMS resonator (1), and is used to track the frequency change of the first-order mode of the MEMS resonator (1) in real time by detecting the phase difference change, and to extract the oscillation amplitude of the first-order mode of the MEMS resonator (1); The input end of the second feedback control circuit (3) is connected to the output end of the first feedback control circuit (2), and the output end of the second feedback control circuit (3) is connected to the feedback control end of the MEMS resonator (1), and is used to output a sideband excitation signal by detecting changes in the oscillation amplitude.

2. The sensor according to claim 1, characterized in that The first feedback control circuit (2) comprises: a transimpedance amplifier circuit (21), an analog-to-digital conversion circuit (22), and a digital phase-locked amplifier circuit (23) connected in sequence, the input end of the transimpedance amplifier circuit (21) serving as the input end of the first feedback control circuit (2), and the output end of the digital phase-locked amplifier circuit (23) serving as the output end of the first feedback control circuit (2); The transimpedance amplifier circuit (21) is used to convert the current generated by the movement of the MEMS resonator (1) into a voltage signal; The analog-to-digital conversion circuit (22) is used to convert the analog signal output by the transimpedance amplifier circuit (21) into a digital signal; The digital phase-locked amplifier circuit (23) is used to read out the oscillation amplitude of the first-order mode of the MEMS resonator (1) and the phase difference between the first-order mode signal of the MEMS resonator (1) and a reference frequency signal, and to track the frequency change of the first-order mode of the MEMS resonator in real time by detecting the change of the phase difference.

3. The sensor according to claim 2, characterized in that The digital phase-locked amplifier circuit (23) comprises: a multiplier, a digital low-pass filter, an amplitude phase demodulator, a first adder, a first PID controller, a second adder and a first digitally controlled oscillator connected in sequence; The input end of the multiplier is connected to the output end of the analog-to-digital conversion circuit and the output end of the first digital controlled oscillator; the first input end of the first adder is connected to the output end of the amplitude phase demodulator The second input terminal of the first adder is connected to the given initial phase shift The first input end of the second adder is connected to the output end of the first PID controller, and the second input end of the second adder is connected to the first given initial center frequency f o ; The multiplier is used to multiply the digital signal output by the analog-to-digital conversion circuit (22) and a pair of orthogonal frequency signals sin and cos output by the first digitally controlled oscillator; The digital low-pass filter is used to filter out the high-frequency signal output by the multiplier; The amplitude phase demodulator is used to demodulate the phase information of the first-order modal frequency signal of the MEMS resonator. and amplitude information A; The first PID controller controls the output frequency of the first digitally controlled oscillator by adjusting the phase information output by the amplitude phase demodulator; The first digital controlled oscillator is regulated by a first PID controller to output a pair of orthogonal signals sin and cos.

4. The sensor according to any one of claims 1 to 3, characterized in that: The second feedback control circuit (3) comprises: a control module (31) and a feedback regulation module (32) connected in sequence; the input end of the control module serves as the input end of the second feedback control circuit (3), and the output end of the feedback regulation module (32) serves as the output end of the second feedback control circuit (3); The control module (31) outputs a control signal for controlling the frequency of the sideband excitation signal by detecting a change in the oscillation amplitude of the first-order mode of the MEMS resonator (1); The feedback regulation module (32) is used to output the sideband excitation signal from the first output end according to the control signal, so that the sensor works in a self-excited oscillation state; and at the same time, extract the frequency information of the sideband excitation signal and output it from the second output end.

5. The sensor according to claim 4, characterized in that The control module (31) uses a lookup table method, a PID regulation method, a linear fitting method or a polynomial fitting regulation method to control the frequency of the sideband excitation signal.

6. The sensor according to claim 5, characterized in that The control module (31) comprises: a third adder, a fourth adder and a second PID controller; The first input end of the third adder is used as the input end of the control module, and the second input end of the third adder is connected to the given initial amplitude offset A o signal, the input end of the second PID controller is connected to the output end of the third adder, the first input end of the fourth adder is connected to the output end of the second PID controller, and the second input end of the fourth adder is used to connect the second given initial center frequency f oo signal, and the output end of the fourth adder serves as the output end of the control module.

7. The sensor according to claim 5, characterized in that The feedback adjustment module (32) comprises: a second digitally controlled oscillator, a digital-to-analog conversion circuit and an amplitude adjustment circuit connected in sequence; The input end of the second digitally controlled oscillator serves as the input end of the feedback regulation module (32), the first output end of the second digitally controlled oscillator serves as the first output end of the feedback regulation module (32), the second output end of the second digitally controlled oscillator serves as the second output end of the feedback regulation module (32), the second digitally controlled oscillator is used to output a sideband excitation signal as a feedback amount, and simultaneously extract frequency information of the sideband excitation signal as a sensing output; The input end of the digital-to-analog conversion circuit is connected to the first output end of the second digitally controlled oscillator, and the digital-to-analog conversion circuit is used to convert the digital signal output by the second digitally controlled oscillator into an analog signal; The input end of the amplitude adjustment circuit is connected to the output end of the digital-to-analog conversion circuit, and the output end of the amplitude adjustment circuit serves as the output end of the feedback adjustment module (32). The amplitude adjustment circuit is used to adjust the amplitude of the sideband excitation signal so that it meets the sideband excitation signal amplitude requirement of the self-excited oscillation of the MEMS resonator.

8. The sensor according to claim 1, characterized in that The MEMS resonator (1) is a resonator with a two-degree-of-freedom two-electrode structure or a resonator with a two-degree-of-freedom four-electrode structure.

9. The sensor according to claim 1, characterized in that The frequency of the sideband excitation signal is equal to a×f p +b×f q , where f p and f q are the p-order and q-order modal eigenfrequencies respectively, p and q are mutually unequal positive integers; a and b are positive integers.

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