Circuits, systems, and methods for mems gyroscope conditioning circuit linearity evaluation

Abstract

The application discloses a circuit, system and method for MEMS gyroscope conditioning circuit linearity evaluation. The circuit simultaneously provides a driving channel signal and a detection channel signal to a gyroscope conditioning circuit chip, the driving channel comprises a first single-ended to differential amplifier receiving a driving signal, a first modulation circuit receiving a timing control signal, and a first capacitor and a second capacitor for outputting the driving channel signal provided by the first capacitor and the second capacitor to simulate a sensitive structure of a MEMS gyroscope; the detection channel comprises a second single-ended to differential amplifier receiving a detection signal, a second modulation circuit receiving the timing control signal, and a third capacitor and a fourth capacitor for outputting the detection channel signal provided by the third capacitor and the fourth capacitor to simulate the sensitive structure of the MEMS gyroscope, so that the linearity test standard of the gyroscope signal conditioning circuit is unified, and the test mode is simpler.

Description

Technical Field

[0001] This invention relates to the field of inertial navigation. More specifically, it relates to a circuit, system, and method for evaluating the linearity of MEMS gyroscope conditioning circuits. Background Technology

[0002] MEMS gyroscopes are core components of inertial navigation systems, offering advantages such as low cost, small size, high precision, and mass production capability. The gyroscope signal conditioning circuit is a crucial component of silicon MEMS gyroscopes. Its working principle involves controlling the sensitive structure of the MEMS gyroscope to maintain a constant amplitude of vibration through a drive loop. Simultaneously, a sensitive detection loop detects minute changes in the sensitive capacitance of the MEMS gyroscope's sensitive structure. This analog signal is then amplified, converted from analog to digital, demodulated, filtered, and compensated before being output as a digital signal through a digital output interface circuit. Therefore, the MEMS gyroscope signal conditioning circuit is a mixed-signal system, comprising analog and digital circuitry, with a memory used to record various circuit configurations and compensation parameters.

[0003] The test method for the linearity of MEMS gyroscope system refers to "Test Method for Microelectromechanical Gyroscopes" (GJB 10024-2021). The MEMS gyroscope is fixed on the angular rate turntable using a mounting fixture. The turntable axis is parallel to the vertical line of the ground, and the alignment accuracy is within a certain number of arcminutes. The input reference axis IRA is parallel to the rotation axis of the angular rate turntable, and the error does not exceed the specified value.

[0004] Currently, the domestic gyroscope signal conditioning circuit industry has transitioned from small-batch or research phase to mass production. However, due to the unique nature of conditioning circuits, the vast majority of gyroscope signal conditioning circuits on the market face the problem of inconsistent testing standards and testing difficulties. Different types of conditioning circuits, due to differences in their internal design, make it difficult to use a unified standard to measure their performance.

[0005] Therefore, there is a need to provide a circuit, system, and method for evaluating the linearity of MEMS gyroscope conditioning circuits. Summary of the Invention

[0006] The purpose of this invention is to provide a circuit, system, and method for evaluating the linearity of MEMS gyroscope conditioning circuits. It addresses the problem of being unable to evaluate the linearity of different types of conditioning circuits in the absence of MEMS gyroscope sensors, and how to use a unified standard to measure circuit performance.

[0007] To achieve at least one of the above objectives, the present invention adopts the following technical solution:

[0008] An equivalent circuit for the output signal of a MEMS gyroscope's sensing structure is disclosed, which simultaneously provides both a drive channel signal and a detection channel signal to the gyroscope conditioning circuit.

[0009] The driving channel includes a first single-ended to differential amplifier for receiving driving signals, a first modulation circuit for receiving timing control signals, and a first capacitor and a second capacitor, which are used to make the outputs of the first capacitor and the second capacitor simulate the driving channel signal provided by the MEMS gyroscope sensing structure.

[0010] The detection channel includes a second single-ended to differential amplifier for receiving the detection signal, a second modulation circuit for receiving the timing control signal, and a third capacitor and a fourth capacitor, which are used to make the output of the third capacitor and the fourth capacitor simulate the detection channel signal provided by the MEMS gyroscope sensing structure.

[0011] Preferably, the first modulation circuit of the driving channel can provide four channels. The first and second channel input ports of the first modulation circuit are respectively connected to the first and second output ports of the first single-ended to differential amplifier. The third and fourth channel input ports of the modulation circuit are connected to ground potential. The first and third channel output ports of the modulation circuit are connected to the input terminal of the first capacitor. The second and fourth channel output ports of the modulation circuit are connected to the input terminal of the second capacitor.

[0012] The second modulation circuit of the detection channel can provide four channels. The first and second channel input ports of the second modulation circuit are respectively connected to the first and second output ports of the second single-ended to differential amplifier. The third and fourth channel input ports of the modulation circuit are connected to ground potential. The first and third channel output ports of the modulation circuit are connected to the input terminal of the third capacitor. The second and fourth channel output ports of the modulation circuit are connected to the input terminal of the fourth capacitor.

[0013] Preferably, the first and second capacitors have the same capacitance value, the third and fourth capacitors have the same capacitance value, and each capacitance value is the same as the corresponding static capacitance value of the MEMS gyroscope sensing structure.

[0014] A system for evaluating the linearity of MEMS gyroscope conditioning circuits includes a signal source, a MEMS gyroscope conditioning circuit, a data acquisition unit, and an equivalent circuit of the MEMS gyroscope sensing structure.

[0015] The signal source is used to provide a detection signal and a drive signal, which have the same resonant frequency and amplitude, but are 90° out of phase.

[0016] The output terminals of the first and second capacitors are respectively connected to the input terminals of the charge-voltage amplifier in the drive loop of the conditioning circuit.

[0017] The output terminals of the third and fourth capacitors are respectively connected to the input terminals of the charge voltage amplifier in the detection loop of the conditioning circuit;

[0018] The data acquisition unit plots a corresponding curve based on the output value of the acquired MEMS gyroscope conditioning circuit and the amplitude of the actual received drive signal, and fits a straight line. Based on the amplitude of the actual received drive signal, the corresponding output value of the acquired MEMS gyroscope conditioning circuit, the fitted straight line, the capacitance gain of the MEMS gyroscope conditioning circuit, and the maximum and minimum values ​​of the capacitance of the gyroscope sensor matched with the conditioning circuit, the nonlinearity of the sensitive angular velocity capacitance gain of the conditioning circuit is determined.

[0019] A method for evaluating the linearity of a MEMS gyroscope conditioning circuit, the method comprising:

[0020] Connect the equivalent circuit of the MEMS gyroscope sensing structure to the MEMS gyroscope conditioning circuit.

[0021] A detection signal and a drive signal are applied to the detection channel and the drive channel, respectively. The detection signal and the drive signal have the same resonant frequency and amplitude, and are 90° out of phase.

[0022] Measure the output of the MEMS gyroscope conditioning circuit;

[0023] Plot a fitted straight line between the drive signal and the output of the conditioning circuit;

[0024] The linearity of the conditioning circuit is evaluated based on the output, the fitted straight line, and the gain of the sensitive angular velocity capacitor of the conditioning circuit.

[0025] Preferably, the method further includes determining the nonlinearity of the sensitive angular velocity capacitance gain of the conditioning circuit based on the maximum and minimum values ​​of the gyroscope sensor capacitance matched to the conditioning circuit of the MEMS gyroscope conditioning circuit.

[0026] Preferably, the nonlinearity K of the sensitive angular velocity capacitor gain of the MEMS gyroscope conditioning circuit is determined according to the following formula. NL Unit: ppm

[0027]

[0028] F j The output value corresponding to the j-th input amplitude of the driving signal;

[0029] The output value on the fitted line corresponding to the j-th input amplitude;

[0030] Kcr For sensitive angular velocity capacitor gain;

[0031] C max The maximum capacitance of the gyroscope sensor that matches the conditioning circuit;

[0032] C min The minimum capacitance of the gyroscope sensor to match the conditioning circuit.

[0033] Preferably, the driving signal is a sine signal, the detection signal is a cosine signal, and the frequency is the resonant frequency of the driving loop in the conditioning circuit.

[0034] Preferably, the amplitude is set sequentially to 0, 10 millivolts, and 100 millivolts, and the corresponding conditioning circuit output value is collected after the circuit stabilizes.

[0035] Preferably, the gain of the sensitive angular velocity capacitor is calculated using the following formula.

[0036]

[0037] in,

[0038] rate is the output of the conditioning circuit; AMP r The input amplitude of the detection signal;

[0039] V H This is the high level of the timing control signal;

[0040] V L This represents the low level of the timing control signal;

[0041] C in1 The static capacitance value of the gyroscope sensor detection channel is matched to the conditioning circuit.

[0042] The beneficial effects of this invention are as follows:

[0043] This paper provides an equivalent circuit for the output signal of a MEMS gyroscope sensing structure, simulating the operating state of a capacitive MEMS gyroscope sensing structure for linearity evaluation of gyroscope conditioning circuits. It also provides a system and method for linearity evaluation of MEMS gyroscope conditioning circuits, unifying the testing standards and simplifying the testing process. For different types of conditioning circuits, it addresses the problem of difficulty in using a unified standard to measure circuit performance due to differences in internal design, providing a unified standard for evaluating circuit performance. Attached Figure Description

[0044] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0045] Figure 1 The diagram shows the working block diagram of a typical MEMS gyroscope and signal conditioning circuit modules.

[0046] Figure 2 The diagram shows the derivation principle of the linearity evaluation method for MEMS gyroscope conditioning circuits of the present invention.

[0047] Figure 3 The schematic diagram of the linearity evaluation method for MEMS gyroscope conditioning circuit of the present invention is shown. Detailed Implementation

[0048] To more clearly illustrate the present invention, the following description, in conjunction with preferred embodiments and accompanying drawings, further explains the invention. Similar components in the drawings are indicated by the same reference numerals. Those skilled in the art should understand that the specific description below is illustrative rather than restrictive and should not be construed as limiting the scope of protection of the present invention.

[0049] In the description of this invention, it should be noted that the terms "upper," "lower," etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Unless otherwise expressly specified and limited, the terms "installed," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication between two elements. For those skilled in the art, the specific meaning of the above terms in this invention can be understood according to the specific circumstances.

[0050] It should also be noted that in the description of this invention, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0051] Currently, the international evaluation of signal conditioning circuits for capacitive gyroscopes typically uses metrics such as equivalent capacitance resolution, linearity, and detection capacitance range.

[0052] like Figure 1 The diagram shows a typical block diagram of a MEMS gyroscope and its signal conditioning circuit modules. The test method for the linearity of the MEMS gyroscope system refers to "GJB 10024-2021 Test Method for Microelectromechanical Gyroscopes". The MEMS gyroscope is fixed on the angular rate turntable using a mounting fixture. The turntable axis is parallel to the vertical line of the ground, and the alignment accuracy is within a certain number of arcminutes. The input reference axis IRA is parallel to the rotation axis of the angular rate turntable, and the error does not exceed the specified value.

[0053] When the sensitive structure senses a change in the external angular velocity, it will deform under the action of the Coriolis force, thereby generating a corresponding change in capacitance.

[0054] Within the range of forward and reverse input angular rates, select at least 11 input angular velocity levels, including the maximum input angular velocity. Set the sampling interval and number of samples for activating the MEMS gyroscope output data according to the product's technical specifications.

[0055] set up For the j-th input angular velocity Ω j The average value of the MEMS gyroscope output is,

[0056]

[0057] In the formula: F jp is the Pth output value of the MEMS gyroscope, and N is the number of samples.

[0058]

[0059] In the formula: This represents the average value of the MEMS gyroscope output when the turntable is stationary.

[0060] This represents the average value of the MEMS gyroscope output at the start of the test.

[0061] This represents the average value of the MEMS gyroscope output at the end of the test.

[0062]

[0063] In the formula: F j For the j-th input angular velocity Ω j At that time, the gyroscope output value.

[0064] Establish a linear model of the input-output relationship of a MEMS gyroscope:

[0065] F j =KΩ j +F0

[0066] In the formula, K is the scaling factor of the MEMS gyroscope, and F0 is the output zero point of the MEMS gyroscope.

[0067] Use the least squares method to find K and F0.

[0068]

[0069]

[0070] In the formula: M is the number of input angular velocities.

[0071] The input-output relationship of a MEMS gyroscope can be represented by a fitted straight line, as shown in the following equation.

[0072]

[0073] In the formula: For the j-th input angular velocity Ω j The MEMS gyroscope output value calculated on the corresponding fitted straight line.

[0074] The point-by-point nonlinear deviation of the MEMS gyroscope output characteristics is calculated using the following formula.

[0075]

[0076] In the formula: a j For the j-th input angular velocity Ω j Nonlinear deviation of MEMS gyroscope output value, in % or ppm.

[0077] F m This represents the maximum absolute value of the gyroscope output at the maximum input angular velocity.

[0078] The scaling factor nonlinearity is calculated using the following formula:

[0079] K n =max|a j |

[0080] Where: K n Scale factor: nonlinearity, expressed in % or ppm.

[0081] This allows us to generate the nonlinear deviation curve of the MEMS gyroscope output (the horizontal axis represents the input angular rate, and the vertical axis represents the nonlinear deviation).

[0082] like Figure 2 As shown, the driving and sensing mass blocks of the sensitive structure can each be equivalent to a pair of differential variable capacitors, with static capacitances of C and C, respectively. 0,d and C 0,sThe gyroscope conditioning circuit chip includes a capacitor / voltage converter (C / V), a voltage amplifier, an analog-to-digital converter (ADC), a band-pass filter (BPF), a low-pass filter (LPF), an amplitude detector, a phase-locked loop (PLL), an automatic gain control (AGC), and a mixer.

[0083] The MEMS gyroscope signal conditioning circuit includes a drive loop and a detection loop. The drive loop, through closed-loop control, ultimately achieves the desired drive resonant frequency ω. d Maintain a constant amplitude A d The resonance of the phase-locked loop results in an output frequency of ω. d Two mutually orthogonal sine and cosine signals are used as demodulation reference signals for the detection path.

[0084] The detection loop detects the capacitance change of the detection mass via a capacitance-to-voltage converter and converts it into a voltage signal. This voltage signal is amplified by a voltage amplifier, converted to a digital signal by an analog-to-digital converter, and then demodulated by the cosine output of a phase-locked loop to generate an output signal *rate* proportional to the applied angular velocity of the gyroscope. The final relationship between the demodulated angular velocity output signal *rate* and the input capacitance change can be expressed as:

[0085]

[0086]

[0087]

[0088] in This represents the phase propagation delay from the input capacitor of the driver-side capacitor-to-voltage converter to the output of the bandpass filter. This represents the phase delay from the Coriolis force (a description of the offset of a particle moving linearly in a rotating system due to inertia relative to the rotating system) to the change in capacitance (related to the Q value of the gyroscope sensor and the resonant frequency). This represents the phase propagation delay from the input capacitor of the sensitive-side capacitor / voltage converter to the output of the bandpass filter. (C) fs For the first-stage feedback capacitor of the sensitive capacitor / voltage converter, g s1 Indicates the gain of the sensitive loop voltage amplifier, g s2 Indicates the normalized voltage gain of the sensitive loop analog-to-digital converter, g s3 The gain of the bandpass filter at the driving resonant frequency is represented by VH and VL, which represent the high and low levels of the EM timing control signal, respectively. r The digital gain of the angular velocity signal is configurable by a register, C. r This indicates the magnitude of the change in sensitive capacitance caused by the Coriolis force.

[0089] make

[0090]

[0091] So

[0092]

[0093] Taking the partial derivative of both sides of the above equation with respect to Cr, we have:

[0094]

[0095] K cr This represents the capacitance gain of the sensitive angular velocity. The above three formulas are the basis for evaluating the gyroscope conditioning circuit independently. As a capacitance detection circuit, it is the most basic and standard test method for evaluating the circuit's ability to handle capacitance. It is worth noting that the capacitance change caused by angular velocity in the gyroscope system is also related to the drive circuit loop parameters. However, in the absence of a gyroscope sensor, the drive loop parameters cannot be correlated with the sensitive loop parameters for testing together; they must be tested separately.

[0096] The relationship between capacitance change and angular velocity can be analyzed as follows:

[0097] C r =Fcor·SNS_F2X·SNS_X2C

[0098] Fcor=2m s ·ω d ·x d ·Ω

[0099]

[0100] C d =x d ·DRV_X2C

[0101] A d =K d ·C d

[0102]

[0103] Where C r The value represents the change in sensitivity caused by the Coriolis force; Fcor represents the Coriolis force; m s For the mass (moment of inertia) of the sensitive mass block, ω d To drive the resonant frequency, SNS_F2X represents the gain caused by the force-induced change in sensitive displacement, determined by the transfer function, ω s For sensitive resonant frequency, Q s For sensitive quality factor, ω inIndicates the frequency of the applied force (when the angular velocity is DC, the frequency of the Coriolis force is equal to the driving resonant frequency), x d SNS_X2C represents the gain of the capacitance change caused by the change in sensitive displacement, DRV_X2C represents the gain of the capacitance change caused by the change in drive displacement, and k represents the gain of the capacitance change caused by the change in drive displacement. yx Indicates the elastic (stiffness) coefficient, C, which is sensitively coupled to the drive. fd For the first stage feedback capacitor of the driver-side capacitor / voltage converter, g d1 Indicates the gain of the second stage of the capacitor / voltage converter at the driver end, g d2 Indicates the normalized voltage gain of the analog-to-digital converter at the driver end, g d3 This represents the gain of the bandpass filter at the driving resonant frequency, C d This indicates the amplitude of the change in the driving end capacitor (both ends), and Ω represents the applied angular velocity (in rad / s).

[0104] Assuming the applied angular velocity is a DC signal, then ω in =ω d Assuming the drive loop operates stably, then Ad = Nref, where Nref is a reference value set via a register. Combining and simplifying the above formulas, we get:

[0105]

[0106] In the formula, the first and second terms on the right are determined by the gyroscope sensor parameters, and the third term is determined by the drive loop parameters.

[0107] Therefore, the angular velocity scale factor K can be obtained. Ω

[0108]

[0109] Where K gyro for

[0110]

[0111] The obtained speed demodulated output signal is

[0112]

[0113] As can be seen from the above formula, the system angular velocity scale factor is mainly determined by the mechanical gain of the gyroscope sensor, the gain ratio of the detection and drive loop, the phase mismatch between the two channels, and the reference value Nref of the automatic gain control.

[0114] It is worth noting the phase mismatch In addition to being related to the mismatch in transmission delay between the two channels, it is also related to the transmission delay of the gyroscope sensor. related, It is mainly determined by the parameters of the gyroscope sensor:

[0115]

[0116] The above analysis shows that the angular velocity scale factor is only related to the gain ratio of the detection and drive loops in the circuit and the phase mismatch between the two channels. Therefore, when evaluating the gyroscope conditioning circuit separately without considering its structure, it is more meaningful to test the capacitance gain of the drive and sensing loops separately. This will give more physical meaning and more directly reflect the performance indicators of the circuit.

[0117] Taking a comb-type MEMS gyroscope as an example, its sensing structure has a basic capacitance of 2pF at a range of 1440° / s, and a maximum capacitance change range of 0.2pF. Therefore, when the angular velocity change reaches 1° / s, the capacitance change is 0.139fF. Since the capacitance change cannot be directly measured, it must be converted. This is based on the fundamental principle of Q=CV.

[0118] ΔC·V EM =ΔV·C noml =ΔQ

[0119] In this formula, ΔC represents the change in capacitance of the sensitive structure when the gyroscope rotates, V EM For modulation voltage, C noml For the capacitor C in the equivalent circuit in1 ΔV represents the equivalent voltage change in the circuit, and ΔQ represents the change in charge during the gyroscope's rotation. Using the above formula, the change in capacitance during gyroscope rotation can be converted into a change in charge, which can then be detected by the conditioning circuit, ultimately achieving system detection.

[0120] In the test method described in this invention, since a continuously changing variable capacitor cannot be obtained during actual testing, a voltage equivalent method is adopted to test the capacitance gain of the circuit.

[0121] Based on the above analysis, such as Figure 2 and Figure 3 The present invention provides an equivalent circuit, system, and method for evaluating the linearity of a gyroscope conditioning circuit.

[0122] In one embodiment of the present invention, an equivalent circuit for the output signal of a MEMS gyroscope sensing structure is provided. This equivalent circuit simultaneously provides a drive channel signal and a detection channel signal to the gyroscope conditioning circuit chip.

[0123] The driving channel includes a first single-ended to differential amplifier for receiving driving signals, a first modulation circuit for receiving timing control signals, and a first capacitor and a second capacitor, which are used to make the outputs of the first capacitor and the second capacitor simulate the driving channel signal provided by the MEMS gyroscope sensing structure.

[0124] The detection channel includes a second single-ended to differential amplifier for receiving the detection signal, a second modulation circuit for receiving the timing control signal, and a third capacitor and a fourth capacitor, which are used to make the output of the third capacitor and the fourth capacitor simulate the detection channel signal provided by the MEMS gyroscope sensing structure.

[0125] In an optional embodiment, the first modulation circuit of the drive channel can provide four channels. The first and second channel input ports of the first modulation circuit are respectively connected to the first and second output ports of the first single-ended to differential amplifier. The third and fourth channel input ports of the modulation circuit are connected to ground potential. The first and third channel output ports of the modulation circuit are connected to the input terminal of the first capacitor. The second and fourth channel output ports of the modulation circuit are connected to the input terminal of the second capacitor.

[0126] The second modulation circuit of the detection channel can provide four channels. The first and second channel input ports of the second modulation circuit are respectively connected to the first and second output ports of the second single-ended to differential amplifier. The third and fourth channel input ports of the modulation circuit are connected to ground potential. The first and third channel output ports of the modulation circuit are connected to the input terminal of the third capacitor. The second and fourth channel output ports of the modulation circuit are connected to the input terminal of the fourth capacitor.

[0127] In an optional embodiment, the first and second capacitors have the same capacitance value, and the third and fourth capacitors have the same capacitance value, each capacitance value being the same as the static capacitance value of the MEMS gyroscope sensing structure.

[0128] In a specific example, in the equivalent circuit of the sensitive structure, the driving channel is a modulation circuit that generates a modulated signal that matches the input. The input single-ended signal is converted by a single-slip amplifier and then input together with the ground potential into the modulation circuit controlled by the EM timing control signal for signal modulation. The output signal is then input to capacitor C in the equivalent circuit. in In section 2, the driving state of the gyroscope during operation is simulated.

[0129] A sinusoidal signal with a 90° phase difference between the input and drive channels is detected. After being amplified by a single-slip amplifier, it is input together with the ground potential into a modulation circuit controlled by the EM timing control signal for signal modulation. The output signal is then input to capacitor C in the equivalent circuit. in1 In the simulation, the detection status of the gyroscope during operation is shown.

[0130] Specifically, the equivalent circuit of the sensitive structure described in this invention can, on the one hand, simulate the working state of the sensitive structure of a capacitive MEMS gyroscope, and on the other hand, generate a modulation timing sequence that matches the conditioning circuit.

[0131] Another embodiment of the present invention provides a system for evaluating the linearity of a MEMS gyroscope conditioning circuit. The system includes a signal source, a MEMS gyroscope conditioning circuit, a data acquisition unit, and an equivalent circuit of the MEMS gyroscope's sensing structure.

[0132] The signal source is used to provide a detection signal and a drive signal, which have the same resonant frequency and amplitude, but are 90° out of phase.

[0133] The output terminals of the first and second capacitors are respectively connected to the input terminals of the charge-voltage amplifier in the drive loop of the conditioning circuit.

[0134] The output terminals of the third and fourth capacitors are respectively connected to the input terminals of the charge voltage amplifier in the detection loop of the conditioning circuit;

[0135] The data acquisition unit plots a corresponding curve based on the output value of the acquired MEMS gyroscope conditioning circuit and the amplitude of the actual received drive signal, and fits a straight line. Based on the amplitude of the actual received drive signal, the corresponding output value of the acquired MEMS gyroscope conditioning circuit, the fitted straight line, the capacitance gain of the MEMS gyroscope conditioning circuit, and the maximum and minimum values ​​of the capacitance of the gyroscope sensor matched with the conditioning circuit, the nonlinearity of the sensitive angular velocity capacitance gain of the conditioning circuit is determined.

[0136] Another embodiment of the present invention provides a method for evaluating the linearity of a MEMS gyroscope conditioning circuit, the method comprising:

[0137] Connect the equivalent circuit of the MEMS gyroscope sensing structure to the MEMS gyroscope conditioning circuit.

[0138] A detection signal and a drive signal are applied to the detection channel and the drive channel, respectively. The detection signal and the drive signal have the same resonant frequency and amplitude, and are 90° out of phase.

[0139] Measure the output of the MEMS gyroscope conditioning circuit;

[0140] Plot a fitted straight line between the drive signal and the output of the conditioning circuit;

[0141] The linearity of the conditioning circuit is evaluated based on the output, the fitted straight line, and the gain of the sensitive angular velocity capacitor of the conditioning circuit.

[0142] In an optional embodiment, the method further includes determining the sensitive angular velocity capacitance gain nonlinearity of the conditioning circuit based on the maximum and minimum values ​​of the gyroscope sensor capacitance matched to the MEMS gyroscope conditioning circuit.

[0143] In an optional embodiment, the sensitive angular velocity capacitor gain nonlinearity K of the MEMS gyroscope conditioning circuit is determined according to the following formula. NL Unit: ppm

[0144]

[0145] F j The output value corresponding to the j-th input amplitude of the driving signal;

[0146] The output value on the fitted line corresponding to the j-th input amplitude;

[0147] K cr For sensitive angular velocity capacitor gain;

[0148] C max The maximum capacitance of the gyroscope sensor that matches the conditioning circuit;

[0149] C min The minimum capacitance of the gyroscope sensor to match the conditioning circuit.

[0150] In an optional embodiment, the driving signal is a sine signal, the detection signal is a cosine signal, and the frequency is the resonant frequency of the driving loop in the conditioning circuit.

[0151] In an optional embodiment, the amplitude is set sequentially to 0, tens of millivolts, and hundreds of millivolts, and the corresponding conditioning circuit output value is collected after the circuit stabilizes.

[0152] In an optional embodiment, the gain of the sensitive angular velocity capacitor is calculated using the following formula.

[0153]

[0154] in,

[0155] rate is the output of the conditioning circuit; AMP r The input amplitude of the detection signal;

[0156] V H This is the high level of the timing control signal;

[0157] V L This represents the low level of the timing control signal;

[0158] C in1 The static capacitance value of the gyroscope sensor detection channel is matched to the conditioning circuit.

[0159] In a specific embodiment, such as Figure 3 As shown in the figure, AMP dAMP represents the amplitude of the sinusoidal signal applied to the driving channel of the equivalent circuit of the sensitive structure, with the phase of the driving signal as a reference. r This represents the amplitude of the cosine signal applied to the detection channel of the equivalent circuit of the sensitive structure, which is also the input amplitude of the detection signal. Therefore, the output of the detection loop (rate) and the output of the amplitude detection module (A) in the drive loop are also considered. d have:

[0160]

[0161]

[0162] This can be simplified to:

[0163]

[0164]

[0165] The equivalent test can determine the gain K of the drive loop capacitor in the circuit. d and the gain K of the sensitive angular velocity demodulation channel capacitor. cr

[0166]

[0167]

[0168] Therefore, by measuring the gain and linearity of the drive amplitude detection output to the voltage amplitude at the drive end, the gain and linearity of the drive loop capacitor can be equivalently calculated and evaluated. Similarly, by measuring the gain and linearity of the sensitive angular velocity demodulation output to the voltage amplitude at the detection end, the gain and linearity of the detection loop capacitor can be equivalently calculated and evaluated.

[0169] The reliability of the equivalent test method is affected by several external conditions. These mainly include the external input capacitance C. in The performance of the input signal source, the single-ended to differential amplifier, phase delay consistency, modulation circuit delay matching, and the influence of parasitic capacitance should be considered during testing. Devices with good temperature characteristics and consistency should be selected whenever possible.

[0170] The linearity of a circuit is defined as the ratio of the maximum deviation of the angular velocity output of the gyroscope conditioning circuit from the least squares fitted straight line to the maximum output within the equivalent input capacitance range.

[0171] Where K d This represents the driving capacitor gain; for ease of recording, the unit can be converted to LSB / fF; K cr Indicates the gain of the sensitive angular velocity capacitor, in units of LSB / fF; A d Indicates the output of the drive amplitude sensing module, in LSB; AMP dThe amplitude of the sinusoidal signal input to the driver terminal is represented in V; rate represents the output value of the sensitive angular velocity demodulation channel, i.e., the output value of the conditioning circuit, in LSB; AMP r This represents the amplitude of the cosine signal applied to the sensitive end, i.e., the input amplitude of the detection signal, expressed in V.

[0172] In a specific example, the test procedure for the gain of the sensitive capacitor is as follows:

[0173] In driving V in,m The end loading frequency is ω d A sinusoidal signal with a fixed amplitude.

[0174] In detecting V in,s The end loading frequency is ω d The cosine signal is used (defined as - if it is 90 degrees out of phase with the drive signal, and + if it is 90 degrees ahead of the drive signal). The amplitude is set to 0, 10 millivolts, and 100 millivolts respectively, with 3 points taken for each level. The output data of the conditioning circuit, i.e., the angular velocity output data, is collected after the circuit stabilizes. The output data is collected for 30 seconds for each input.

[0175] The experimental data and the fitted straight line are used to calculate the nonlinearity of the sensitive angular velocity capacitor gain according to the following formula:

[0176]

[0177] F j The output value corresponding to the j-th input amplitude of the driving signal;

[0178] The output value on the fitted line corresponding to the j-th input amplitude;

[0179] K cr For sensitive angular velocity capacitor gain;

[0180] C max The maximum capacitance of the gyroscope sensor that matches the conditioning circuit;

[0181] C min Minimum capacitance of the gyroscope sensor to match the conditioning circuit;

[0182] K NL The gain of the capacitor with sensitive angular velocity is nonlinear, and the unit is ppm.

[0183] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all the implementation methods here. All obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A system for evaluating the linearity of MEMS gyroscope conditioning circuits, characterized in that, The system includes a signal source, a MEMS gyroscope conditioning circuit, a data acquisition unit, and an equivalent circuit for the output signal of the MEMS gyroscope's sensing structure. The equivalent circuit of the output signal of the MEMS gyroscope's sensing structure simultaneously provides both the drive channel signal and the detection channel signal to the gyroscope conditioning circuit. The driving channel includes a first single-ended to differential amplifier that receives driving signals, a first modulation circuit that receives timing control signals, and a first capacitor and a second capacitor, which are used to make the outputs of the first capacitor and the second capacitor simulate the driving channel signals provided by the MEMS gyroscope sensing structure. The detection channel includes a second single-ended to differential amplifier for receiving the detection signal, a second modulation circuit for receiving the timing control signal, and a third capacitor and a fourth capacitor, which are used to make the output of the third capacitor and the fourth capacitor simulate the detection channel signal provided by the MEMS gyroscope sensing structure. The signal source is used to provide a detection signal and a drive signal, which have the same resonant frequency and amplitude, but are 90° out of phase. The output terminals of the first and second capacitors are respectively connected to the input terminals of the charge voltage amplifier in the drive loop of the conditioning circuit. The output terminals of the third and fourth capacitors are respectively connected to the input terminals of the charge voltage amplifier in the detection loop of the conditioning circuit; The data acquisition unit plots a corresponding curve based on the output value of the acquired MEMS gyroscope conditioning circuit and the amplitude of the actual received drive signal, and fits a straight line. Based on the amplitude of the actual received drive signal, the corresponding output value of the acquired MEMS gyroscope conditioning circuit, the fitted straight line, the capacitance gain of the MEMS gyroscope conditioning circuit, and the maximum and minimum values ​​of the capacitance of the gyroscope sensor matched with the conditioning circuit, the nonlinearity of the sensitive angular velocity capacitance gain of the conditioning circuit is determined. The capacitance gain is obtained in a voltage equivalent manner.

2. The system according to claim 1, characterized in that, The first modulation circuit of the driving channel can provide four channels. The first and second channel input ports of the first modulation circuit are respectively connected to the first and second output ports of the first single-ended to differential amplifier. The third and fourth channel input ports of the modulation circuit are connected to ground potential. The first and third channel output ports of the modulation circuit are connected to the input terminal of the first capacitor. The second and fourth channel output ports of the modulation circuit are connected to the input terminal of the second capacitor. The second modulation circuit of the detection channel can provide four channels. The first and second channel input ports of the second modulation circuit are respectively connected to the first and second output ports of the second single-ended to differential amplifier. The third and fourth channel input ports of the modulation circuit are connected to ground potential. The first and third channel output ports of the modulation circuit are connected to the input terminal of the third capacitor. The second and fourth channel output ports of the modulation circuit are connected to the input terminal of the fourth capacitor.

3. The system according to claim 1, characterized in that, The first and second capacitors have the same capacitance value, and the third and fourth capacitors have the same capacitance value. Each capacitance value is the same as the corresponding static capacitance value of the MEMS gyroscope sensing structure.

4. A method for evaluating the linearity of a MEMS gyroscope conditioning circuit, characterized in that, The method includes: Connect the equivalent circuit of the output signal of the MEMS gyroscope sensitive structure in the system according to claim 1 to the MEMS gyroscope conditioning circuit. A detection signal and a drive signal are applied to the detection channel and the drive channel, respectively. The detection signal and the drive signal have the same resonant frequency and amplitude, and are 90° out of phase. Measure the output of the MEMS gyroscope conditioning circuit; Plot a fitted straight line between the drive signal and the output of the conditioning circuit; The linearity of the conditioning circuit is evaluated based on the output, the fitted straight line, and the gain of the sensitive angular velocity capacitor of the conditioning circuit.

5. The method for evaluating the linearity of a MEMS gyroscope conditioning circuit according to claim 4, characterized in that, The method further includes determining the sensitive angular velocity capacitance gain nonlinearity of the conditioning circuit based on the maximum and minimum values ​​of the gyroscope sensor capacitance matched to the MEMS gyroscope conditioning circuit.

6. The method for evaluating the linearity of a MEMS gyroscope conditioning circuit according to claim 5, characterized in that, The nonlinearity of the sensitive angular velocity capacitor gain of the MEMS gyroscope conditioning circuit is determined according to the following formula. K NL Unit: ppm F j The output value corresponding to the j-th input amplitude of the driving signal; The output value on the fitted line corresponding to the j-th input amplitude; For sensitive angular velocity capacitor gain; The maximum capacitance of the gyroscope sensor that matches the conditioning circuit; The minimum capacitance of the gyroscope sensor to match the conditioning circuit.

7. The method for evaluating the linearity of a MEMS gyroscope conditioning circuit according to claim 6, characterized in that, The driving signal is a sine signal, the detection signal is a cosine signal, and the frequency is the resonant frequency of the driving loop in the conditioning circuit.

8. The method for evaluating the linearity of a MEMS gyroscope conditioning circuit according to claim 6, characterized in that, The amplitude is set sequentially to 0, 10 millivolts, and 100 millivolts, and the corresponding conditioning circuit output value is collected after the circuit stabilizes.

9. The method for evaluating the linearity of a MEMS gyroscope conditioning circuit according to claim 6, characterized in that, Calculate the gain of the sensitive angular velocity capacitor using the following formula. in, For the output of the conditioning circuit; The input amplitude of the detection signal; This is the high level of the timing control signal; V L This represents the low level of the timing control signal; C in1 The static capacitance value of the gyroscope sensor detection channel is matched to the conditioning circuit.

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