MEMS capacitive accelerometer resonant frequency point test system and method

Abstract

The invention provides a system and a method for testing a resonant frequency point of an MEMS capacitive accelerometer. The test system comprises a control module, a preprocessing module, a detection module and an extraction module. The control module is used for generating a driving signal and changing the frequency of the driving signal at a certain step length in the testing process; the preprocessing module is used for preprocessing the driving signal and applying the processed signal to the N end of the accelerometer; the detection module is used for converting an output signal received from the P end of the accelerometer into a detection signal and providing the detection signal to the control module; the control module is also used for performing signal processing on the detection signal to obtain a signal amplitude; the extraction module is used for extracting the resonant frequency of the accelerometer based on the signal amplitude. Based on a capacitor structure and a working principle of the MEMS capacitive accelerometer, two input ends of the MEMS capacitive accelerometer are respectively used as a driving end and a detection end, and the test of the resonant frequency point of the accelerometer is accurately and efficiently completed through the input of a driving signal and the detection and processing of an output signal.

Description

Technical Field

[0001] The present invention relates to the technical field of accelerometer systems, and in particular to a resonant frequency point testing system and method for a MEMS capacitive accelerometer. Background Art

[0002] MEMS accelerometers are key components of inertial navigation systems and are mainly used to measure the acceleration of carriers. Among the many types of accelerometers, MEMS capacitive accelerometers have been widely used in biomedicine, consumer electronics, automobiles, robotics, military and other fields due to their significant advantages such as low noise, low power consumption, high accuracy and insensitivity to temperature changes.

[0003] The resonant frequency of a MEMS capacitive accelerometer is a key design and application parameter. It not only determines the range and sensitivity of the accelerometer, but also directly affects its stability and reliability. Therefore, it is crucial to accurately measure the resonant frequency of a MEMS capacitive accelerometer. At present, the resonant frequency of a MEMS capacitive accelerometer is usually obtained through theoretical design values ​​and simulations. However, due to device processing errors and device losses, the actual resonant frequency will deviate from the theoretical value. This deviation will result in a large error between the resonant frequency obtained by the existing method and the actual resonant frequency, thereby affecting the measurement accuracy, stability, accuracy, and dynamic response performance of the accelerometer. Summary of the invention

[0004] The present invention provides a MEMS capacitive accelerometer resonant frequency point testing system and method, which are used to solve the problem in the prior art that the actual resonant frequency point of the MEMS capacitive accelerometer cannot be accurately obtained.

[0005] The present invention provides a MEMS capacitive accelerometer resonant frequency point testing system, comprising a control module, a preprocessing module, a detection module and an extraction module; The control module is configured to generate a driving signal and output the driving signal; The preprocessing module is configured to receive the driving signal, preprocess the driving signal, and apply the preprocessed driving signal to the N terminal of the MEMS capacitive accelerometer; The detection module is configured to receive an output signal from a P terminal of the MEMS capacitive accelerometer, convert the output signal into a detection signal, and provide the detection signal to the control module; The control module is further configured to receive a detection signal from the detection module, perform signal processing on the detection signal to obtain a signal amplitude, and provide the signal amplitude to the extraction module; The extraction module is configured to extract the resonant frequency of the MEMS capacitive accelerometer based on the signal amplitude; Wherein, during the test process, the control module changes the frequency of the driving signal with a certain step size.

[0006] In some embodiments, the control module includes: a digitally controlled oscillator and a control unit; The digital controlled oscillator is configured to generate one half-frequency sine and two full-frequency sine according to a half-frequency sine code table and a full-frequency sine code table respectively; the frequency of the one half-frequency sine is half of the frequency of each of the two full-frequency sines, the amplitude of the one half-frequency sine and the two full-frequency sine are the same, and the phase difference between the two full-frequency sine is 90°; The control unit is configured to perform digital-to-analog conversion on the half-frequency sine wave and output it as the driving signal, and The control unit is further configured to perform analog-to-digital conversion on the detection signal provided by the detection module to obtain a digital detection signal; perform in-phase demodulation and quadrature demodulation on the digital detection signal based on the two full-frequency sinusoidal signals to generate an in-phase component and a quadrature component; perform notch processing and filtering on the in-phase component and the quadrature component; calculate the amplitude based on the in-phase component and the quadrature component after the notch processing and the filtering processing to obtain the signal amplitude and provide the signal amplitude to the extraction module.

[0007] In some embodiments, the pre-processing module includes a DC isolator; and the pre-processing includes DC isolation processing.

[0008] In some embodiments, the pre-processing module further includes an amplifier; and the pre-processing further includes signal amplification processing.

[0009] In some embodiments, the detection module includes: a detection unit and an anti-aliasing filtering unit; The detection unit is configured to receive an output signal from a P terminal of the MEMS capacitive accelerometer, convert the output signal into a voltage signal, and provide the voltage signal to the anti-aliasing filtering unit, wherein the output signal is a capacitive signal; The anti-aliasing filtering unit is configured to perform anti-aliasing filtering processing on the voltage signal, and provide the processed voltage signal as the detection signal to the control module.

[0010] The present invention also provides a method for testing the resonant frequency point of a MEMS capacitive accelerometer, comprising: generating a driving signal; Preprocessing the driving signal; Applying the preprocessed driving signal to the N terminal of the MEMS capacitive accelerometer; Receiving an output signal from a P terminal of a MEMS capacitive accelerometer and converting the output signal into a detection signal; Performing signal processing on the detection signal to obtain a signal amplitude; Based on the signal amplitude, extracting a resonant frequency of the MEMS capacitive accelerometer; During the test, the frequency of the driving signal is changed in a certain step size.

[0011] In some embodiments, the generating the driving signal comprises: generating one half-frequency sine and two full-frequency sine according to a half-frequency sine code table and a full-frequency sine code table respectively, and performing digital-to-analog conversion on the one half-frequency sine as the driving signal; the frequency of the one half-frequency sine is half of the frequency of each of the two full-frequency sines, the amplitude of the one half-frequency sine is the same as the amplitude of the two full-frequency sines, and the phase difference between the two full-frequency sines is 90°; The signal processing of the detection signal includes: performing analog-to-digital conversion on the detection signal to obtain a digital detection signal; performing in-phase demodulation and quadrature demodulation on the digital detection signal based on the two full-frequency sinusoidal signals to generate an in-phase component and a quadrature component; performing notch processing and filtering on the in-phase component and the quadrature component; and calculating the signal amplitude based on the in-phase component and the quadrature component after the notch processing and the filtering processing.

[0012] In some embodiments, the pre-processing includes a DC isolation process.

[0013] In some embodiments, the preprocessing further includes signal amplification processing.

[0014] In some embodiments, converting the output signal received from the P-terminal of the MEMS capacitive accelerometer into a detection signal includes: converting the output signal received from the P-terminal of the MEMS capacitive accelerometer into a voltage signal, and performing anti-aliasing filtering on the voltage signal to obtain the detection signal, wherein the output signal is a capacitive signal.

[0015] The present invention is based on the capacitor structure and working principle of a MEMS capacitive accelerometer, utilizes two differential input terminals of the accelerometer, uses one terminal as a driving terminal to apply a driving signal with a frequency changed in a certain step length, and uses the other terminal as a detection terminal to detect an output signal, converts the output signal into a detection signal, obtains a signal amplitude through signal processing, and based on the fact that the signal amplitude changes with the change of the driving signal frequency, a resonance peak appears when the driving signal frequency reaches the resonant frequency point of the accelerometer, and extracts the resonant frequency of the accelerometer according to the resonance peak, thereby completing accurate testing of the resonant frequency point of the accelerometer. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0017] Figure 1 It is a schematic diagram of the comb structure of a MEMS capacitive accelerometer; Figure 2 It is a schematic diagram of the detection principle of the MEMS capacitive accelerometer; Figure 3 It is a schematic diagram of a single comb capacitor of a MEMS capacitive accelerometer without a loaded signal; Figure 4 This is a schematic diagram of a single comb capacitor of a MEMS capacitive accelerometer after loading a signal; Figure 5 is a schematic block diagram of a resonant frequency point testing system for a MEMS capacitive accelerometer according to an embodiment of the present invention; Figure 6 1. It is a schematic diagram of digital code representation of half-frequency sine signal and full-frequency sine signal of the resonant frequency point test system of the MEMS capacitive accelerometer according to an embodiment of the present invention; Figure 7 is a schematic block diagram of a resonant frequency point testing system for a MEMS capacitive accelerometer according to another embodiment of the present invention; Figure 8 is a signal processing principle diagram of a resonant frequency point test system of a MEMS capacitive accelerometer according to an embodiment of the present invention; Fig. 9 is a flow chart of a method for testing a resonant frequency point of a MEMS capacitive accelerometer according to an embodiment of the present invention; Fig.10 is a schematic diagram of a resonant frequency point test result of a MEMS capacitive accelerometer according to an embodiment of the present invention; Fig.11 is a schematic structural diagram of an electronic device according to an embodiment of the present invention. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions in the present invention will be clearly and completely described below in conjunction with the drawings in the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. It should be noted that the embodiments of the present invention and the features in the embodiments can be combined with each other in the absence of conflict. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0019] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0020] It should be further noted that, in this article, the terms "comprises", "includes" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the sentence "comprises a ..." does not exclude the presence of other identical elements in the process, method, article or device including the element.

[0021] In the present invention, "at least one" means one or more, and "more" means two or more than two. The terms "first", "second", "third", "fourth", etc. (if any) in the present invention are used to distinguish similar objects, rather than to describe a specific order or sequence.

[0022] In the embodiments of the present invention, words such as "exemplary" or "for example" are used to indicate examples, illustrations or explanations. Any embodiment or design described as "exemplary" or "for example" in the embodiments of the present invention should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of words such as "exemplary" or "for example" is intended to present related concepts in a specific way.

[0023] In order to facilitate a clearer understanding of the embodiments of the present invention, some relevant technical knowledge is first introduced as follows.

[0024] Figure 1 This is a schematic diagram of the comb structure of a MEMS capacitive accelerometer. Figure 2 This is a schematic diagram of the detection principle of the MEMS capacitive accelerometer. Figure 1 and Figure 2Describe the comb structure and measurement principle of MEMS capacitive accelerometer. Figure 1 The MEMS capacitive accelerometer adopts a comb structure 100, including a substrate 101, a mass block 102, a movable comb tooth 103, a fixed comb tooth 104 and an elastic member 105. The mass block 102 is connected to the substrate 101 through the elastic member 105, the movable comb tooth 103 is fixedly connected to the mass block 102, the fixed comb tooth 104 is fixedly connected to the substrate 101, and the movable comb teeth and the fixed comb teeth are arranged alternately. When acceleration acts on the mass block 102, the mass block 102 will be displaced and drive the movable comb teeth 103 to move, thereby causing the relative position between the movable comb teeth 103 and the fixed comb teeth 104 to change, thereby causing a change in capacitance. This capacitance change is processed by a signal amplification and conditioning circuit to achieve acceleration measurement.

[0025] refer to Figure 1 and Figure 2 Specifically, the MEMS capacitive accelerometer is driven by a sinusoidal carrier. First, the DAC module of the ARM chip generates a sinusoidal signal. After circuit processing, two voltage references, sinusoidal signals with the same amplitude and frequency and a phase difference of 180° (for example, +Vc and -Vc) are obtained. The two signals are loaded onto the two differential electrodes of the accelerometer. When the acceleration is sensitive, the mass block will be displaced due to the acceleration, causing the capacitance between the plates to change (for example, C1 and C2), generating differential capacitance (for example, Cf). The signal amplification and conditioning circuit converts the differential capacitance signal into a voltage signal (for example, Uo), and finally obtains the acceleration information to complete the detection.

[0026] Figure 3 and Figure 4 It is a schematic diagram of the structure of a single comb-tooth capacitor in the comb-tooth design structure of the MEMS accelerometer, where Figure 3 Shows the case where no driving signal is loaded. Figure 4 It shows the situation after the driving signal is loaded. Figure 5 is a schematic block diagram of a resonant frequency point test system according to an embodiment of the present invention. Figure 3 , Figure 4 and Figure 5 Embodiments according to the present invention are described.

[0027] refer to Figure 3 In a single comb-tooth capacitor structure, when no signal is loaded, the comb-tooth plates are distributed as follows: Figure 3 As shown, the middle is a movable comb-tooth pole plate COM, and the two sides are fixed comb-tooth pole plates N and P. The two fixed comb-tooth pole plates N and P are equidistant from the movable comb-tooth pole plate COM, which is d0.

[0028] refer to Figure 5The resonant frequency point testing system provided by the present invention includes a control module 210 , a preprocessing module 220 , a detection module 230 and an extraction module 240 .

[0029] The control module 210 is used to generate a driving signal and provide the driving signal to the pre-processing module 220 , and at the same time, during the test process, the frequency of the driving signal is changed with a certain step length.

[0030] The preprocessing module 220 is used to receive the driving signal, preprocess the driving signal, and apply the preprocessed driving signal to the N terminal of the MEMS capacitive accelerometer.

[0031] The detection module 230 is used to convert the output signal received from the P terminal of the MEMS capacitive accelerometer into a detection signal based on the driving signal, and provide the detection signal to the control module 210 .

[0032] The control module 210 is further configured to receive a detection signal from the detection module 230 , perform signal processing on the detection signal to obtain a signal amplitude, and provide the signal amplitude to the extraction module 240 .

[0033] The extraction module 240 is used to extract the resonant frequency of the MEMS capacitive accelerometer based on the signal amplitude.

[0034] refer to Figure 4 During the test, when the driving signal is loaded to the N terminal of the MEMS capacitive accelerometer, that is, loaded to the fixed comb-tooth plate N, the fixed comb-tooth plate N and the movable comb-tooth plate COM generate an electrostatic force F e , the electrostatic force causes the movable comb-tooth pole plate COM to move, and the moving distance is x. At this time, due to the movement of the movable comb-tooth pole plate COM, a variable capacitance is formed between the movable comb-tooth pole plate COM and the fixed comb-tooth pole plate P. At this time, the capacitance value is as shown in the following equation: …… ... Wherein, C is the variable capacitance between the movable comb-tooth pole plate COM and the fixed comb-tooth pole plate P, ε is the dielectric constant of the capacitance, S is the orthographic overlapping area of ​​the fixed comb-tooth pole plate P and the movable comb-tooth pole plate COM in the direction perpendicular to the pole plate plane, d0 is the initial distance between the movable comb-tooth pole plate COM and any one of the fixed comb-tooth pole plates N and P when the driving signal is not loaded, and x is the distance moved by the movable comb-tooth pole plate COM after the driving signal is loaded.

[0035] Taylor expands the above equation into: …… (2) Wherein, C is the variable capacitance between the movable comb-tooth pole plate COM and the fixed comb-tooth pole plate P, ε is the dielectric constant of the capacitance, S is the orthographic overlapping area of ​​the fixed comb-tooth pole plate P and the movable comb-tooth pole plate COM in the direction perpendicular to the pole plate plane, d0 is the initial distance between the movable comb-tooth pole plate COM and any one of the fixed comb-tooth pole plates N and P when the driving signal is not loaded, and x is the distance moved by the movable comb-tooth pole plate COM after the driving signal is loaded.

[0036] Since the displacement x generated by the electrostatic force is much smaller than the comb teeth spacing, that is, , so the above formula ignores the high-order terms and becomes: ………… (3) Wherein, C is the variable capacitance between the movable comb-tooth plate COM and the fixed comb-tooth plate P, ε is the dielectric constant of the capacitance, S is the orthographic overlap area of ​​the fixed comb-tooth plate P and the movable comb-tooth plate COM in the direction perpendicular to the plate plane, d0 is the initial distance between the movable comb-tooth plate COM and any one of the fixed comb-tooth plates N and P when no driving signal is loaded, x is the distance moved by the movable comb-tooth plate COM after the driving signal is loaded, ∆C is the capacitance change, and C0 is the capacitance between the movable comb-tooth plate COM and the fixed comb-tooth plate P when no driving signal is loaded.

[0037] From the above formula, it can be obtained that the capacitance change ∆C is proportional to the displacement of the movable comb plate COM, as shown in the following formula: …… ... Where ∆C is the capacitance change, ε is the dielectric constant of the capacitor, S is the overlapping area of ​​the orthographic projection of the fixed comb-tooth plate P and the movable comb-tooth plate COM in the direction perpendicular to the plate plane, d0 is the initial distance between the movable comb-tooth plate COM and the fixed comb-tooth plate P when no driving signal is loaded, and x is the distance moved by the movable comb-tooth plate COM after the driving signal is loaded.

[0038] Through the P end of the MEMS capacitive accelerometer, ie, the fixed comb-tooth plate P, the detection module 230 can detect the capacitance change.

[0039] During the test, the control module 210 changes the frequency of the driving signal with a certain step length. Taking the driving signal as a half-frequency sine signal as an example, the electrostatic force generated between the movable comb-tooth plate COM and the fixed comb-tooth plate N is expressed as follows: …… ... In the formula, F e is the electrostatic force between the movable comb plate COM and the fixed comb plate N, V ac is the driving signal amplitude, w is the driving signal angular frequency, and t is time.

[0040] Because the electrostatic force moves the movable comb-tooth pole plate COM, a variable capacitance is generated between the movable comb-tooth pole plate COM and the fixed comb-tooth pole plate P. The detection module 230 detects and converts the signal of the fixed comb-tooth pole plate P, and the detection signal V0 is obtained as shown below: …… ... Where V0 is the detection signal, ∆q is the charge change, Cf is the feedback capacitance of the detection module 230, ∆C is the capacitance change, V d A bias voltage is provided for the detection module 230 .

[0041] The electrostatic force is proportional to the displacement. Combining with formula (4), it can be concluded that the detection signal V0 is a signal with the same frequency as the electrostatic force, and the amplitude of the detection signal V0 is proportional to the amplitude of the fixed comb plate P. Therefore, as the frequency of the driving signal changes with a certain step size, the amplitude of the detection signal will also change. When it reaches the resonant frequency point of the accelerometer, the amplitude of the detection signal is the largest.

[0042] The control module 210 receives the detection signal from the detection module 230 , performs signal processing on the detection signal to obtain a signal amplitude, and provides the signal amplitude to the extraction module 240 .

[0043] The extraction module 240 obtains Fig.10 The results shown show that an obvious resonance peak appears during the frequency sweep process. The resonance peak has a maximum amplitude, and the resonance frequency point of the MEMS capacitive accelerometer corresponds to twice the horizontal axis. The extraction module extracts the resonance frequency.

[0044] The present invention is based on the capacitor structure and working principle of a MEMS capacitive accelerometer, utilizes two differential input terminals of the accelerometer, uses one terminal as a driving terminal to apply a driving signal with a frequency changed in a certain step length, and uses the other terminal as a detection terminal to detect an output signal, converts the output signal into a detection signal, obtains a signal amplitude through signal processing, and based on the fact that the signal amplitude changes with the change of the driving signal frequency, a resonance peak appears when the driving signal frequency reaches the resonant frequency point of the accelerometer, extracts the resonant frequency of the accelerometer according to the resonance peak, and completes accurate testing of the resonant frequency point of the accelerometer.

[0045] Figure 7 is a schematic block diagram of a test system according to another embodiment of the present invention, Figure 8 1 is a signal processing principle diagram of a test system according to an embodiment of the present invention. Figure 7 and Figure 8 The signal processing of the test system according to the embodiment of the present invention is described.

[0046] In some embodiments, Figure 7As shown, the control module 210 includes a numerically controlled oscillator (NCO) 211 and a control unit 212 .

[0047] The digital controlled oscillator 211 is configured to generate one half-frequency sine and two full-frequency sine according to the half-frequency sine code table and the full-frequency sine code table, respectively. The frequency of the one half-frequency sine is half of the frequency of each of the two full-frequency sines, the amplitude of the one half-frequency sine and the two full-frequency sine are the same, and the phase difference between the two full-frequency sine is 90°. The digital code table of the half-frequency sine signal and the full-frequency sine signal is as follows: Figure 6 As shown, Figure 6 The upper part is the digital code table of full-frequency sine signal, and the lower part is the digital code table of half-frequency sine signal.

[0048] The control unit 212 is configured to perform digital-to-analog conversion on the half-frequency sine wave and output it as a driving signal, and is further configured to perform analog-to-digital conversion on the detection signal provided by the detection module to obtain a digital detection signal; perform in-phase demodulation and quadrature demodulation on the digital detection signal based on the two full-frequency sine waves to generate an in-phase component and a quadrature component; perform notch processing and filtering on the in-phase component and the quadrature component; calculate the amplitude based on the in-phase component and the quadrature component after the notch processing and filtering processing, obtain the signal amplitude and provide the signal amplitude to the extraction module 240.

[0049] Specifically, Figure 8 As shown, the half-frequency sine code table generated by the digital control oscillator 211 generates an analog half-frequency sine carrier signal as a driving signal through digital-to-analog conversion in the control unit 212. The driving signal is pre-processed by the pre-processing module 220 and applied to the N terminal of the MEMS capacitive accelerometer. The detection module 230 detects the output signal of the P terminal at the P terminal of the MEMS capacitive accelerometer, converts it into a detection signal V0, and provides the detection signal V0 to the control unit 212 in the control module 210. The detection signal V0 is demodulated after being converted by analog to digital by the control unit 212.

[0050] The signal to be demodulated is: …………(7) …… ... Where w is the angular frequency, n is the number of discrete sampling points, T is the sampling period, A is the signal amplitude, and A TX is the amplitude of the in-phase component, A ZJ is the amplitude of the orthogonal component, The rotation angle introduced by the circuit and program can be obtained and compensated by calculation outside the lower computer program.

[0051] Multiplying the demodulated signal of equation (7) with the two full-frequency sinusoidal demodulated signals generated by the digitally controlled oscillator (NCO) yields the following result: With demodulated signal Multiplying them gives the in-phase components: …… (9) Where A0 is the demodulated signal amplitude, w is the angular frequency, n is the number of discrete sampling points, T is the sampling period, and A TX is the amplitude of the in-phase component, A ZJ is the amplitude of the orthogonal component.

[0052] With demodulated signal Multiplying them gives the orthogonal components: …… (10) Where A0 is the demodulated signal amplitude, w is the angular frequency, n is the number of discrete sampling points, T is the sampling period, and A TX is the amplitude of the in-phase component, A ZJ is the amplitude of the orthogonal component.

[0053] It can be seen from the demodulated in-phase component and quadrature component that the detection signal includes a DC component and an AC component after modulation, and a double frequency appears at the same time, but the demodulated signal and the baseband signal may also be coupled with some DC noise signals, so the control unit 212 further performs notch processing on the baseband and the double frequency, and then filters out other clutter through a low-pass filter, retaining the DC component and filtering out other AC components. The control unit 212 performs amplitude calculation based on the in-phase component and the quadrature component after notch processing and filtering, and provides the calculation result to the extraction module 240.

[0054] In some embodiments, the pre-processing module 220 includes a DC block 221 for performing DC block processing on the driving signal output by the control module 210 to remove possible DC signals in the driving signal.

[0055] In some embodiments, the pre-processing module 220 further includes an amplifier 222 for amplifying the driving signal.

[0056] In some embodiments, the detection module 230 includes a detection unit 231 and an anti-aliasing filter unit 232. The detection unit 231 is configured to convert the capacitance signal received from the P terminal of the MEMS capacitive accelerometer into a voltage signal, and provide the voltage signal to the anti-aliasing filter unit 232; the anti-aliasing filter unit 232 is configured to perform anti-aliasing filtering on the voltage signal, and provide the processed voltage signal as the detection signal V0 to the control unit 212 in the control module 210.

[0057] In some embodiments, the control unit 212 is further configured to perform automatic gain control (AGC) on the signal before performing digital-to-analog conversion on the half-frequency sinusoidal signal to stabilize the amplitude of the signal.

[0058] In some embodiments, the detection signal V0 may be transmitted to the control module 210 via, for example, SPI communication.

[0059] The following is a description of a method for testing the resonant frequency point of a MEMS capacitive accelerometer provided by the present invention. The method for testing the resonant frequency point of a MEMS capacitive accelerometer described below and the system for testing the resonant frequency point of a MEMS capacitive accelerometer described above can refer to each other.

[0060] Fig. 9 is a flow chart of a testing method according to an embodiment of the present invention, referring to Fig. 9 The present invention provides a method for testing the resonant frequency point of a MEMS capacitive accelerometer. The execution subject is a testing system for the resonant frequency point of the MEMS capacitive accelerometer. The method includes: Step S910: Generate a driving signal, and during the test, change the frequency of the driving signal in a certain step size.

[0061] Step S920: preprocess the driving signal, and apply the preprocessed driving signal to the N terminal of the MEMS capacitive accelerometer.

[0062] Step S930: receiving an output signal from the P terminal of the MEMS capacitive accelerometer, and converting the output signal into a detection signal.

[0063] Step S940: Process the detection signal to obtain the signal amplitude.

[0064] Step S950: extracting the resonant frequency of the MEMS capacitive accelerometer based on the signal amplitude.

[0065] like Fig.10As shown in the signal amplitude results, an obvious resonance peak appears during the frequency sweep process, and the resonance frequency point of the MEMS capacitive accelerometer is corresponding to twice the horizontal axis at the maximum amplitude of the resonance peak.

[0066] The present invention is based on the capacitor structure and working principle of a MEMS capacitive accelerometer, utilizes two differential input terminals of the accelerometer, uses one terminal as a driving terminal to apply a driving signal with a frequency changed in a certain step length, and uses the other terminal as a detection terminal to detect an output signal, converts the output signal into a detection signal, obtains a signal amplitude through signal processing, and based on the fact that the signal amplitude changes with the change of the driving signal frequency, a resonance peak appears when the driving signal frequency reaches the resonant frequency point of the accelerometer, and extracts the resonant frequency of the accelerometer according to the resonance peak, thereby completing accurate testing of the resonant frequency point of the accelerometer.

[0067] In some embodiments, generating the driving signal includes: generating one half-frequency sine and two full-frequency sine according to a half-frequency sine code table and a full-frequency sine code table, respectively, and performing digital-to-analog conversion on the one half-frequency sine as the driving signal for output. The frequency of the one half-frequency sine is half of the frequency of each of the two full-frequency sines, the amplitude of the one half-frequency sine is the same as the amplitude of the two full-frequency sines, and the phase difference between the two full-frequency sines is 90°.

[0068] In some embodiments, signal processing of the detection signal includes: performing analog-to-digital conversion on the detection signal to obtain a digital detection signal; performing in-phase demodulation and quadrature demodulation on the digital detection signal based on two full-frequency sinusoidal signals to generate an in-phase component and a quadrature component; performing notch processing and filtering on the in-phase component and the quadrature component; calculating the signal amplitude based on the in-phase component and the quadrature component after the notch processing and filtering, and outputting the calculation result.

[0069] In some embodiments, the pre-processing includes performing DC isolation processing on the driving signal to remove possible DC signals in the driving signal.

[0070] In some embodiments, the preprocessing further includes signal amplification processing to improve the measurement accuracy of the resonance frequency point.

[0071] In some embodiments, converting the output signal received from the P terminal of the MEMS capacitive accelerometer into a detection signal includes: converting the capacitance signal received from the P terminal of the MEMS capacitive accelerometer into a voltage signal, and performing anti-aliasing filtering on the voltage signal to obtain the detection signal.

[0072] In some embodiments, before performing digital-to-analog conversion on a half-frequency sine wave, automatic gain control (AGC) is performed on the half-frequency sine wave to stabilize the amplitude of the signal.

[0073] The present invention can be applied not only to MEMS capacitive accelerometers, but also to other devices, apparatuses or equipment having a comb-teeth capacitor structure similar to that of MEMS capacitive accelerometers.

[0074] Fig.11 is a schematic diagram of the structure of an electronic device according to an embodiment of the present invention. Fig.11 As shown, the electronic device may include: a processor 1110, a communication interface 1120, a memory 1130 and a communication bus 1140, wherein the processor 1110, the communication interface 1120 and the memory 1130 communicate with each other through the communication bus 1140. The processor 1110 may call the logic instructions in the memory 1130 to execute a method for testing the resonant frequency point of a MEMS capacitive accelerometer, the method comprising: generating a driving signal, and in the test process, changing the frequency of the driving signal by a certain step length; preprocessing the driving signal; applying the preprocessed driving signal to the N-terminal of the MEMS capacitive accelerometer; converting the output signal received from the P-terminal of the MEMS capacitive accelerometer into a detection signal; performing signal processing on the detection signal to obtain a signal amplitude; and extracting the resonant frequency of the MEMS capacitive accelerometer based on the signal amplitude.

[0075] In addition, the logic instructions in the above-mentioned memory 1130 can be implemented in the form of a software functional unit and can be stored in a computer-readable storage medium when it is sold or used as an independent product. Based on such an understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art or the part of the technical solution, can be embodied in the form of a software product, and the computer software product is stored in a storage medium, including a number of instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk, etc. Various media that can store program codes.

[0076] On the other hand, the present invention also provides a computer program product, which includes a computer program. The computer program can be stored on a non-transitory computer-readable storage medium. When the computer program is executed by a processor, the computer can execute the test method for the resonant frequency point of the MEMS capacitive accelerometer provided by the above methods, and the method includes: generating a drive signal, and during the test, changing the frequency of the drive signal with a certain step size; preprocessing the drive signal; applying the preprocessed drive signal to the N-terminal of the MEMS capacitive accelerometer; converting the output signal received from the P-terminal of the MEMS capacitive accelerometer into a detection signal; performing signal processing on the detection signal to obtain a signal amplitude; and extracting the resonant frequency of the MEMS capacitive accelerometer based on the signal amplitude.

[0077] On the other hand, the present invention also provides a non-transitory computer-readable storage medium having a computer program stored thereon. When the computer program is executed by a processor, it is implemented to execute the test method of the resonant frequency point of the MEMS capacitive accelerometer provided by the above-mentioned methods, the method comprising: generating a drive signal, and during the test, changing the frequency of the drive signal by a certain step size; preprocessing the drive signal; applying the preprocessed drive signal to the N-terminal of the MEMS capacitive accelerometer; converting the output signal received from the P-terminal of the MEMS capacitive accelerometer into a detection signal; performing signal processing on the detection signal to obtain a signal amplitude; and extracting the resonant frequency of the MEMS capacitive accelerometer based on the signal amplitude.

[0078] The device embodiments described above are merely illustrative, wherein the units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, they may be located in one place, or they may be distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the scheme of this embodiment. Ordinary technicians in this field can understand and implement it without paying creative labor.

[0079] Through the description of the above implementation methods, those skilled in the art can clearly understand that each implementation method can be implemented by means of software plus a necessary general hardware platform, and of course, can also be implemented by hardware. Based on this understanding, the above technical solution is essentially or the part that contributes to the prior art can be embodied in the form of a software product, and the computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, a disk, an optical disk, etc., including a number of instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in each embodiment or some parts of the embodiments.

[0080] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A MEMS capacitive accelerometer resonant frequency point testing system, characterized in that: It includes a control module, a preprocessing module, a detection module and an extraction module; The control module is configured to generate a driving signal and output the driving signal; The preprocessing module is configured to receive the driving signal, preprocess the driving signal, and apply the preprocessed driving signal to the N terminal of the MEMS capacitive accelerometer; The detection module is configured to receive an output signal from a P terminal of the MEMS capacitive accelerometer, convert the output signal into a detection signal, and provide the detection signal to the control module; The control module is further configured to receive a detection signal from the detection module, perform signal processing on the detection signal to obtain a signal amplitude, and provide the signal amplitude to the extraction module; The extraction module is configured to extract the resonant frequency of the MEMS capacitive accelerometer based on the signal amplitude; Wherein, during the test process, the control module changes the frequency of the driving signal with a certain step size.

2. The test system according to claim 1, characterized in that: The control module includes: a digitally controlled oscillator and a control unit; The digital controlled oscillator is configured to generate one half-frequency sine and two full-frequency sine according to a half-frequency sine code table and a full-frequency sine code table respectively; the frequency of the one half-frequency sine is half of the frequency of each of the two full-frequency sines, the amplitude of the one half-frequency sine and the two full-frequency sine are the same, and the phase difference between the two full-frequency sine is 90°; The control unit is configured to perform digital-to-analog conversion on the half-frequency sine wave and output it as the driving signal, and The control unit is further configured to perform analog-to-digital conversion on the detection signal provided by the detection module to obtain a digital detection signal; perform in-phase demodulation and quadrature demodulation on the digital detection signal based on the two full-frequency sinusoidal signals to generate an in-phase component and a quadrature component; perform notch processing and filtering on the in-phase component and the quadrature component; calculate the amplitude based on the in-phase component and the quadrature component after the notch processing and the filtering processing to obtain the signal amplitude and provide the signal amplitude to the extraction module.

3. The test system according to claim 1 or 2, characterized in that: The preprocessing module includes a DC isolator; the preprocessing includes DC isolation processing.

4. The test system according to claim 3, characterized in that: The preprocessing module further includes an amplifier; the preprocessing further includes signal amplification processing.

5. The test system according to claim 1 or 2, characterized in that: The detection module comprises: a detection unit and an anti-aliasing filtering unit; The detection unit is configured to receive an output signal from a P terminal of the MEMS capacitive accelerometer, convert the output signal into a voltage signal, and provide the voltage signal to the anti-aliasing filtering unit, wherein the output signal is a capacitive signal; The anti-aliasing filtering unit is configured to perform anti-aliasing filtering processing on the voltage signal, and provide the processed voltage signal as the detection signal to the control module.

6. A method for testing the resonant frequency point of a MEMS capacitive accelerometer, characterized in that: include: generating a driving signal; Preprocessing the driving signal; Applying the preprocessed driving signal to the N terminal of the MEMS capacitive accelerometer; Receiving an output signal from a P terminal of a MEMS capacitive accelerometer and converting the output signal into a detection signal; Performing signal processing on the detection signal to obtain a signal amplitude; Based on the signal amplitude, extracting a resonant frequency of the MEMS capacitive accelerometer; During the test, the frequency of the driving signal is changed in a certain step size.

7. The testing method according to claim 6, characterized in that: The generating of the driving signal comprises: generating one half-frequency sine and two full-frequency sine according to a half-frequency sine code table and a full-frequency sine code table respectively, and performing digital-to-analog conversion on the one half-frequency sine as the driving signal; the frequency of the one half-frequency sine is half of the frequency of each of the two full-frequency sines, the amplitude of the one half-frequency sine is the same as the amplitude of the two full-frequency sines, and the phase difference between the two full-frequency sines is 90°; The signal processing of the detection signal includes: performing analog-to-digital conversion on the detection signal to obtain a digital detection signal; performing in-phase demodulation and quadrature demodulation on the digital detection signal based on the two full-frequency sinusoidal signals to generate an in-phase component and a quadrature component; performing notch processing and filtering on the in-phase component and the quadrature component; and calculating the signal amplitude based on the in-phase component and the quadrature component after the notch processing and the filtering processing.

8. The testing method according to claim 6 or 7, characterized in that: The pre-processing includes a DC isolation process.

9. The testing method according to claim 8, characterized in that: The preprocessing further includes signal amplification processing.

10. The testing method according to claim 6 or 7, characterized in that: The step of converting the output signal received from the P terminal of the MEMS capacitive accelerometer into a detection signal includes: converting the output signal received from the P terminal of the MEMS capacitive accelerometer into a voltage signal, and performing anti-aliasing filtering on the voltage signal to obtain the detection signal, wherein the output signal is a capacitive signal.

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