阅读说明：本技术 一种mems谐振器闭环控制方法及控制结构 (MEMS resonator closed-loop control method and control structure ) 是由 王玉朝 滕霖 于 2021-09-10 设计创作，主要内容包括：本申请提供一种MEMS谐振器闭环控制方法及控制结构,其中,MEMS谐振器闭环控制结构包括了控制振幅的AGC环路8和控制相位的PLL环路13。其中PLL环路13包括了鉴相器9、环路滤波器10、压控振荡器11和1/2分频器12。驱动/检测方法是通过将PLL环路13的压控振荡器11的输出信号经过1/2分频器12进行分频处理,输出两路正交的1f信号,经过驱动电极全差分设计,能够在MEMS谐振器上施加频率为2f的驱动静电力,并使得MEMS谐振器工作在2f谐振状态,实现了倍频驱动。这样就将驱动信号的频率1f和检测信号的频率2f在频域上实现了分离,消除了驱动信号作为电气串扰源对检测的影响；而且1f正交驱动信号无直流偏置电压,避免了偏置电压漂移对MEMS谐振器性能的影响。(The application provides a closed-loop control method and a control structure of a MEMS resonator, wherein the closed-loop control structure of the MEMS resonator comprises an AGC loop 8 for controlling amplitude and a PLL loop 13 for controlling phase. Where the PLL loop 13 comprises a phase detector 9, a loop filter 10, a voltage controlled oscillator 11 and a frequency divider 12 of 1/2. The driving/detecting method is that the output signal of the voltage-controlled oscillator 11 of the PLL loop 13 is subjected to frequency division processing through a 1/2 frequency divider 12, two paths of orthogonal 1f signals are output, and through the full-differential design of a driving electrode, a driving electrostatic force with the frequency of 2f can be applied to the MEMS resonator, so that the MEMS resonator works in a 2f resonance state, and frequency multiplication driving is realized. Therefore, the frequency 1f of the driving signal is separated from the frequency 2f of the detection signal in the frequency domain, and the influence of the driving signal as an electrical crosstalk source on the detection is eliminated; and the 1f orthogonal driving signal has no direct current bias voltage, so that the influence of bias voltage drift on the performance of the MEMS resonator is avoided.)

1. The MEMS (Micro-electro mechanical Systems) resonator closed-loop control structure is characterized by comprising an MEMS resonator (1), a C/V converter (2), an AGC (automatic Gain control) loop (8), a PLL (phase Locked loop) loop (13), a first multiplier (14) and a second multiplier (15); the AGC loop (8) comprises a rectifier (3), a low-pass filter (4), an adder (5), a PI (Proportional-Integral) controller (6) and a reference datum (7); the PLL loop (13) comprises a phase detector (9), a loop filter (10), a voltage controlled oscillator (11) and a 1/2 frequency divider (12), wherein:

the output of the first multiplier (14) and the output of the second multiplier (15) are respectively connected with the input of the MEMS resonator (1), the output of the MEMS resonator (1) is connected with the input of the C/V converter (2), and the output of the C/V converter (2) is respectively connected with the rectifier (3) and the phase detector (9); the rectifier (3) is respectively connected with the input of a first multiplier (14) and the input of a second multiplier (15) through a low-pass filter (4), an adder (5) and a PI controller (6); the phase detector (9) is respectively connected with the input of a first multiplier (14) and the input of a second multiplier (15) through a loop filter (10), a voltage-controlled oscillator (11) and an 1/2 frequency divider (12) in sequence; the reference base (7) is connected with the positive input of the adder (5); the output of the low-pass filter (4) is connected with the negative input of the adder (5); and a second quadrature input signal end of the voltage-controlled oscillator (11) is connected with the input of the phase detector (9).

2. The MEMS resonator closed-loop control structure according to claim 1, characterized in that the drive and sense electrodes of the MEMS resonator (1) are mechanically fully differential structural morphology.

3. A MEMS resonator closed-loop control method, applied to the MEMS resonator closed-loop control structure of claim 1, the method comprising:

1/2 the frequency divider (12) outputs a first quadrature signal to the first multiplier (14) and a second quadrature signal to the second multiplier (15), wherein the first quadrature signal and the second quadrature signal are 90 degrees out of phase;

a first multiplier (14) amplitude modulates the first quadrature signal to obtain a first drive signal v₊Outputting a first drive signal v to the negative input of the MEMS resonator 1₊(ii) a The second multiplier (15) performs amplitude modulation on the second orthogonal signal to obtain a second driving signal v_-Outputting a second drive signal v to the positive input terminal of the MEMS resonator 1_-；

After orthogonal driving with the frequency of a preset signal frequency F, the MEMS resonator 1 generates a driving electrostatic force F, wherein the frequency of the driving electrostatic force F is 2F;

the MEMS resonator 1 generates an alternating capacitor C with the frequency of 2F according to the driving electrostatic force F, and outputs the alternating capacitor C to the C/V converter 2;

converting the alternating capacitor C into a voltage signal V through a C/V converter 2 so as to complete the detection of the 2f differential capacitor;

a voltage signal V output by the C/V converter 2 is divided into a first path of voltage signal and a second path of voltage signal, the first path of voltage signal is input to the rectifier 3, and the second path of voltage signal is input to the phase discriminator 9;

performing AGC processing on the first path of voltage signal to obtain an amplitude modulation signal A, and outputting the amplitude modulation signal A to a first multiplier (14) and a second multiplier (15) respectively to be used as amplitude modulation signals of a first orthogonal signal and a second orthogonal signal;

performing PLL processing on the second path of voltage signal to generate a first orthogonal input signal and a second orthogonal input signal, wherein the second orthogonal input signal is fed back to the phase detector 9 to serve as the other path of input signal of the phase detector;

the voltage-controlled oscillator 11 inputs the generated first quadrature input signal and second quadrature input signal to the 1/2 frequency divider 12;

1/2 frequency divider 12 generates a first quadrature signal and a second quadrature signal of a predetermined signal frequency f and feeds the first quadrature signal and the second quadrature signal back to first multiplier (14) and second multiplier (15), respectively, thereby completing the closed-loop control of the MEMS resonator.

4. The method of claim 3, wherein the phase of the first quadrature signal is cos (2 π ft); the phase of the second quadrature signal is sin (2 π ft).

5. The method of claim 3, wherein the phase of the first quadrature input signal is cos (4 π ft); the phase of the second quadrature input signal is sin (4 π ft).

6. A method according to claim 3, characterized in that the preset signal frequency f is half the main resonance frequency of the MEMS resonator 1.

7. The method according to claim 3, wherein performing AGC processing on the first path voltage signal to obtain an amplitude modulation signal a specifically includes:

the first path of voltage signal passes through the rectifier 3 and the low-pass filter 4 in sequence, and is subtracted by a reference signal output by a reference 7 through an adder 5, and then is input to a PI controller 6, and an amplitude modulation signal A is generated.

8. The method of claim 3, wherein the PLL processing the second path of voltage signal to generate a first quadrature input signal and a second quadrature input signal comprises:

the second path of voltage signal passes through the phase detector 9, the loop filter 10 and the voltage-controlled oscillator 11 in sequence to generate a first orthogonal input signal and a second orthogonal input signal.

Technical Field

The invention belongs to the MEMS resonator closed-loop control technology, and particularly relates to an MEMS resonator closed-loop control method and a control structure.

Background

The MEMS resonator, as a type of device, includes a resonance type MEMS sensor that can measure various physical quantities, such as a vibrating silicon micro gyroscope, a resonance type pressure sensor, a resonance type accelerometer, a MEMS time base, and the like. The MEMS resonator usually needs to be driven in a resonant state, and a closed-loop control circuit is established through a specific driving and detecting mode, which becomes a basic means for realizing the working state of the MEMS resonator. While the driving and detecting mode of a typical MEMS resonator processed based on a silicon structure MEMS process is usually electrostatic driving/capacitance detection.

In order to improve the linearity of electrostatic driving, the driving signal is usually set to be in-phase direct current + differential alternating current or in-phase alternating current + differential direct current, so that a single-frequency signal can be generated, and energy concentration of the driving signal is realized. However, as the electrostatic driving/capacitance detection MEMS resonator, the driving signal is easily interfered to the detection end due to the influence of parasitic and coupling capacitance at the chip level, electrical crosstalk at the board level, and the like, which affects the detection accuracy. In order to solve the problem, a "Drive Amplitude dependency of micro reactor Series mechanical Resistance" published by Jun Cao et al of michigan university in the united states has first proposed an Electromechanical Amplitude Modulation (EAM) technique to eliminate electrical crosstalk, but this method needs to add a carrier signal on a driving end or a mass block, needs to perform secondary demodulation on a detecting end, and increases the complexity of a circuit. In the document "Parasitic feedback compensation for enhanced electrical characteristics of electrostatic resonators" published by the university of cambridge, england, j.e. -y.lee et al, it is proposed to provide a dummy resonator beside the MEMS resonator and to apply a reverse drive signal to the dummy resonator in order to generate a reverse electrical crosstalk signal, so that mutual cancellation of the electrical crosstalk error signals at the detection end is achieved. But this approach loses on the one hand the area utilization of the chip; on the other hand, the effect of the electric crosstalk compensation can be influenced by the inconsistency of the lining MEMS resonator and the MEMS resonator processing.

Disclosure of Invention

In order to realize a closed-loop control circuit of an MEMS resonator, drive the MEMS resonator to resonate and eliminate the influence of electric crosstalk on a detection signal, a closed-loop control method and a control structure of the resonator based on 1f orthogonal drive 2f frequency multiplication detection are provided.

In a first aspect, the present application provides a MEMS (Micro-electro mechanical Systems) resonator closed-loop control structure, which includes a MEMS resonator 1, a C/V converter 2, an agc (automatic Gain control) loop 8, a pll (phase Locked loop) loop 13, a first multiplier 14, and a second multiplier 15; the AGC loop 8 comprises a rectifier 3, a low pass filter 4, an adder 5, a PI (Proportional-Integral) controller 6, a reference 7; the PLL loop 13 comprises a phase detector 9, a loop filter 10, a voltage controlled oscillator 11 and a frequency divider 1/2 12, wherein:

the output of the first multiplier 14 and the output of the second multiplier 15 are respectively connected with the input of the MEMS resonator 1, the output of the MEMS resonator 1 is connected with the input of the C/V converter 2, and the output of the C/V converter 2 is respectively connected with the rectifier 3 and the phase discriminator 9; the rectifier 3 is respectively connected with the input of a first multiplier 14 and the input of a second multiplier 15 through a low-pass filter 4, an adder 5 and a PI controller 6 in sequence; the phase detector 9 is respectively connected with the input of a first multiplier 14 and the input of a second multiplier 15 through a loop filter 10, a voltage-controlled oscillator 11 and a 1/2 frequency divider 12 in sequence; the reference base 7 is connected to the positive input of the adder 5; the output of the low-pass filter 4 is connected with the negative input of the adder 5; a second quadrature input signal terminal of the voltage controlled oscillator 11 is connected to an input of the phase detector 9.

Preferably, the drive electrode and the detection electrode of the MEMS resonator 1 are mechanically fully differential.

In a second aspect, the present application provides a MEMS resonator closed-loop control method, which is applied to the MEMS resonator closed-loop control structure of claim 1, the method comprising:

1/2 divider 12 outputs a first quadrature signal to a first multiplier (14) and a second quadrature signal to a second multiplier (15), wherein the first quadrature signal and the second quadrature signal are 90 degrees out of phase;

a first multiplier (14) amplitude modulates the first quadrature signal to obtain a first drive signal v₊Outputting a first drive signal v to the negative input of the MEMS resonator 1₊(ii) a The second multiplier (15) performs amplitude modulation on the second orthogonal signal to obtain a second driving signal v_-Outputting a second drive signal v to the positive input terminal of the MEMS resonator 1_-；

After orthogonal driving with the frequency of a preset signal frequency F, the MEMS resonator 1 generates a driving electrostatic force F, wherein the frequency of the driving electrostatic force F is 2F;

the MEMS resonator 1 generates an alternating capacitor C with the frequency of 2F according to the driving electrostatic force F, and outputs the alternating capacitor C to the C/V converter 2;

converting the alternating capacitor C into a voltage signal V through a C/V converter 2 so as to complete the detection of the 2f differential capacitor;

a voltage signal V output by the C/V converter 2 is divided into a first path of voltage signal and a second path of voltage signal, the first path of voltage signal is input to the rectifier 3, and the second path of voltage signal is input to the phase discriminator 9;

performing AGC processing on the first path of voltage signal to obtain an amplitude modulation signal A, respectively outputting the amplitude modulation signal A to a first multiplier (14) and a second multiplier (15), and using the amplitude modulation signal A as a first orthogonal signal and a second orthogonal signal;

performing PLL processing on the second path of voltage signal to generate a first orthogonal input signal and a second orthogonal input signal, wherein the second orthogonal input signal is fed back to the phase detector 9 to serve as the other path of input signal of the phase detector;

the voltage-controlled oscillator 11 inputs the generated first quadrature input signal and second quadrature input signal to the 1/2 frequency divider 12;

1/2 frequency divider 12 generates a first quadrature signal and a second quadrature signal at a predetermined signal frequency f and feeds the first quadrature signal and the second quadrature signal back to first multiplier (14) and second multiplier (15), respectively, thereby completing the closed-loop control of the MEMS resonator.

Preferably, the phase of the first quadrature signal is cos (2 pi ft); the phase of the second quadrature signal is sin (2 π ft).

Preferably, the phase of the first quadrature input signal is cos (4 π ft); the phase of the second quadrature input signal is sin (4 π ft).

Preferably, the preset signal frequency f is half the main resonance frequency of the MEMS resonator 1.

Preferably, performing AGC processing on the first path of voltage signal to obtain an amplitude modulation signal a specifically includes:

the first path of voltage signal passes through the rectifier 3 and the low-pass filter 4 in sequence, and is subtracted by a reference signal output by a reference 7 through an adder 5, and then is input to a PI controller 6, and an amplitude modulation signal A is generated.

Preferably, the PLL processing the second path of voltage signal to generate a first quadrature input signal and a second quadrature input signal specifically includes:

the second path of voltage signal passes through the phase detector 9, the loop filter 10 and the voltage-controlled oscillator 11 in sequence to generate a first orthogonal input signal and a second orthogonal input signal.

The invention has the advantages that: the provided MEMS resonator closed-loop control method based on 1f orthogonal driving 2f frequency multiplication detection is characterized in that a 1f orthogonal driving signal is applied to a differential driving electrode to generate a 2f driving electrostatic force on an MEMS resonator, so that the MEMS resonator is driven to realize 2f frequency multiplication displacement and 2f frequency multiplication capacitance change, a driving alternating current signal and a detection capacitance signal are separated in a frequency domain, the influence of an electrical crosstalk signal of 1f on the detection signal is completely eliminated, and the precision and the signal-to-noise ratio of signal detection are improved; and the driving voltage is a pure alternating current signal without direct current bias voltage, so that the influence of bias voltage drift on the performance of the MEMS resonator is avoided.

Drawings

FIG. 1 is a functional block diagram of a structure of a closed-loop control circuit of an MEMS resonator based on 1f orthogonal driving 2f frequency doubling detection, which is provided by the invention;

wherein: the circuit comprises a 1-MEMS resonator, a 2-C/V converter, a 3-rectifier, a 4-low-pass filter, a 5-adder, a 6-PI controller, a 7-reference, a 9-phase detector, a 10-loop filter, an 11-voltage-controlled oscillator, a 12-1/2 frequency divider, a 14-first multiplier, a 15-second multiplier, an 8-AGC loop and a 13-PLL loop.

Detailed Description

Example one

As shown in fig. 1, the present application provides a MEMS resonator closed-loop control structure including a MEMS resonator 1, a C/V converter 2, an AGC loop 8, a PLL loop 13, a first multiplier 14, and a second multiplier 15; the AGC loop 8 comprises a rectifier 3, a low-pass filter 4, an adder 5, a PI controller 6 and a reference datum 7; the PLL loop 13 comprises a phase detector 9, a loop filter 10, a voltage controlled oscillator 11 and a frequency divider 12 of 1/2.

The output of the first multiplier 14 and the output of the second multiplier 15 are respectively connected with the input of the MEMS resonator 1, the output of the MEMS resonator 1 is connected with the input of the C/V converter 2, and the output of the C/V converter 2 is respectively connected with the rectifier 3 and the phase discriminator 9; the rectifier 3 is respectively connected with the input of a first multiplier 14 and the input of a second multiplier 15 through a low-pass filter 4, an adder 5 and a PI controller 6 in sequence; the phase detector 9 is respectively connected with the input of a first multiplier 14 and the input of a second multiplier 15 through a loop filter 10, a voltage-controlled oscillator 11 and a 1/2 frequency divider 12 in sequence; the reference base 7 is connected to the positive input of the adder 5; the output of the low-pass filter 4 is connected with the negative input of the adder 5; a second quadrature input signal terminal of the voltage controlled oscillator 11 is connected to an input of the phase detector 9.

The drive electrode and the detection electrode of the controlled-object MEMS resonator are in a fully-differential structure in terms of mechanical structure.

It can be understood that the working principle of the MEMS resonator closed-loop control structure provided by the present application is as follows:

the mechanical movement of the MEMS resonator 1 results in a change of the capacitance C, which is converted from capacitance to voltage by the C/V converter 2. The output voltage V of the C/V converter 2 is divided into two paths, one path enters an AGC loop 8, the ac signals are rectified by a rectifier 3, low-pass filtering is performed by a low-pass filter 4, amplitude extraction of the ac signals is completed, a reference 7 outputs a voltage corresponding to a target amplitude, the voltage and the output of the low-pass filter 4 enter an adder 5 at the same time, subtraction operation is performed, an error voltage is obtained, and the error voltage is output to a first multiplier 14 and a second multiplier 15 as an amplitude modulation signal a of driving ac after passing through a PI controller 6. The other path of the output voltage V of the C/V converter 2 enters a PLL loop 13, and passes through a phase detector 9, a loop filter 10, a voltage controlled oscillator 11, and a 1/2 frequency divider 12, respectively, wherein a second quadrature input signal output by the voltage controlled oscillator 11 is fed back to the phase detector 10, and is compared with the output voltage of the C/V converter 3 in phase, so as to output a phase error signal, which is filtered by the loop filter 10 and output to the voltage controlled oscillator 11, and the output signals of the voltage controlled oscillator 11, namely a first quadrature input signal cos (4 π ft) and a second quadrature input signal sin (4 π ft), are controlled to be output as two paths of quadrature signals, namely a first quadrature signal cos (2 π ft) and a second quadrature signal sin (2 π ft), by the 1/2 frequency divider 12, and are input as a 1f quadrature driving voltage to a first multiplier 14 and a second multiplier 15, respectively, after multiplying the amplitude modulation signal a output from the PI controller 6, the multiplied signal is input to the drive electrode of the MEMS resonator 1 in the fully differential configuration.

Example two

The following further describes the embodiments of the present invention with reference to the drawings.

A mathematical description of the structure of the MEMS resonator closed-loop control circuit shown in figure 1 is established. The application provides a closed-loop control method of an MEMS resonator, which comprises the following steps:

the method comprises the following steps: 1/2 the frequency divider 12 outputs a first quadrature signal with a phase cos (2 π ft) to the first multiplier 14 and a second quadrature signal with a phase sin (2 π ft) to the second multiplier 15;

step two: the first multiplier 14 performs amplitude modulation on the first quadrature signal to obtain a first driving signal v₊Outputting a first drive signal v to the negative input of the MEMS resonator 1₊(ii) a The second multiplier (15) performs amplitude modulation on the second orthogonal signal to obtain a second driving signal v_-Outputting a second drive signal v to the positive input terminal of the MEMS resonator 1_-；

It should be noted that the preset signal frequency of the MEMS resonator closed-loop control structure is f.

It can be seen that the first drive signal v₊And a second drive signal v_-The MEMS resonator is used as two driving signals of a fully differential structure of the MEMS resonator so as to realize the orthogonal driving of the MEMS resonator.

Step three: after orthogonal driving with the frequency of a preset signal frequency F, the MEMS resonator 1 generates a driving electrostatic force F, wherein the frequency of the driving electrostatic force F is 2F;

it should be noted that the two paths of quadrature signals output by the 1/2 frequency divider 12, the first quadrature signal and the second quadrature signal are cos (2 PI ft) and sin (2 PI ft), respectively, the output of the PI controller 6 is an amplitude modulation signal a, and the capacitance between the driving electrodes of the MEMS resonator 1 is C_dThe driving electrostatic force F applied to the MEMS resonator 1 is:

that is, after the MEMS resonator 1 is orthogonally driven at 1f, a driving electrostatic force of 2f is generated.

Step four: the MEMS resonator 1 generates an alternating capacitance C with a frequency of 2F according to the driving electrostatic force F, and outputs the alternating capacitance C to the C/V converter 2.

Specifically, the MEMS resonator 1 drives the MEMS resonator 1 to oscillate at a frequency point of 2F according to the generated driving electrostatic force F, thereby generating an alternating capacitance C with a frequency of 2F;

step five: converting the alternating capacitor C into a voltage signal V through a C/V converter 2 so as to complete the detection of the 2f differential capacitor;

step six: a voltage signal V output by the C/V converter 2 is divided into a first path of voltage signal and a second path of voltage signal, the first path of voltage signal is input to the rectifier 3, and the second path of voltage signal is input to the phase discriminator 9;

step seven: the first path of voltage signal passes through the rectifier 3 and the low-pass filter 4 in sequence, and is subtracted by a reference signal output by a reference 7 through an adder 5, and then is input into a PI controller 6; the PI controller 6 outputs the generated amplitude modulation signal a to the first multiplier 14 and the second multiplier 15, respectively, and outputs the amplitude modulation signals as a first quadrature signal and a second quadrature signal;

step eight: the second path of voltage signal passes through the phase detector 9, the loop filter 10 and the voltage-controlled oscillator 11 in sequence to generate a first orthogonal input signal cos (4 pi ft) and a second orthogonal input signal sin (4 pi ft), wherein the second orthogonal input signal is fed back to the phase detector 9 and serves as the other path of input signal of the phase detector;

step nine: the voltage controlled oscillator 11 inputs the generated first quadrature input signal cos (4 pi ft) and second quadrature input signal sin (4 pi ft) to the 1/2 frequency divider 12;

step ten: 1/2 frequency divider 12 generates a first quadrature signal and a second quadrature signal at a predetermined signal frequency f and feeds the first quadrature signal and the second quadrature signal back to first multiplier (14) and second multiplier (15), respectively, thereby completing the closed-loop control of the MEMS resonator.

For example, if the output amplitude modulation signal a of the PI controller 6 is 2V, the first driving signal V applied to the driving electrode₊2cos (2 pi × 5000) (V), second drive signal V_-2sin (2 pi × 5000) (V), drive end capacitance C_pGradient for displacement x of 3.6X 10^-8(F/m), the resulting driving electrostatic force F is:

therefore, for the MEMS resonator with the resonant frequency of 10kHz, the frequency of two paths of alternating current driving signals is 5kHz, and the frequency of the generated driving electrostatic force F is 10kHz, so that the closed-loop resonant driving of the MEMS resonator is realized, and the resonant working state of the MEMS resonator is ensured; the frequency of the alternating current driving signal is separated from the frequency of the detection capacitance signal in a frequency domain, and electrical crosstalk is eliminated.

In summary, the present invention belongs to the MEMS resonator closed-loop control technology, and in particular, relates to a MEMS resonator closed-loop control method based on 1f quadrature drive 2f frequency multiplication detection. The MEMS resonator closed-loop control structure comprises an MEMS resonator closed-loop control structure form and a driving/detecting method. Wherein the MEMS resonator closed loop control structure includes an AGC loop 8 to control amplitude and a PLL loop 13 to control phase. Where the PLL loop 13 comprises a phase detector 9, a loop filter 10, a voltage controlled oscillator 11 and a frequency divider 12 of 1/2. The driving/detecting method is that the frequency of the output signal of the voltage-controlled oscillator 11 of the PLL loop 13 is divided by the 1/2 frequency divider 12 to output two paths of orthogonal 1f signals, and the driving electrostatic force with the frequency of 2f can be applied to the MEMS resonator through the full-differential design of the driving electrode, so that the MEMS resonator works in the 2f resonance state, and the frequency doubling driving is realized. Therefore, the frequency 1f of the driving signal is separated from the detection signal 2f in the frequency domain, and the influence of the driving signal as an electrical crosstalk source on detection is eliminated; and the 1f orthogonal driving signal has no direct current bias voltage, so that the influence of bias voltage drift on the performance of the MEMS resonator is avoided.