CN-122017285-A - Signal processing method and system of micro-electromechanical system capacitive accelerometer

CN122017285ACN 122017285 ACN122017285 ACN 122017285ACN-122017285-A

Abstract

The embodiment of the application provides a signal processing method and a system of a capacitive accelerometer of a micro-electromechanical system, wherein the method comprises the steps of detecting capacitance change caused by acceleration through a differential capacitance structure to obtain differential capacitance change, inputting the differential capacitance change into a transimpedance amplifier, converting the differential capacitance change into voltage change data, superposing the voltage change data with direct-current bias voltage to generate a baseband modulation signal, generating a square wave carrier signal by a square wave carrier generating unit, modulating the baseband modulation signal and the square wave carrier signal to generate a modulation signal, synchronously demodulating the modulation signal by an annular diode demodulation circuit and outputting two paths of signals, carrying out low-pass filtering on the two paths of signals to filter high-frequency carrier components and keep low-frequency acceleration signals, carrying out differential operation on the two paths of filtered signals, outputting a target voltage signal in linear relation with the acceleration, and maintaining constant gain conversion of a signal processing link.

Inventors

Shan Yuanhao
WANG YINGZE
Feng Kaichen
HONG LI
LI XIAO
YANG NING
WANG ZHIQIANG

Assignees

中国电子科技集团公司信息科学研究院

Dates

Publication Date: 20260512
Application Date: 20251211

Claims (10)

1. A method for processing signals of a capacitive accelerometer of a microelectromechanical system, comprising: detecting capacitance change caused by acceleration through a differential capacitance structure to obtain differential capacitance change quantity ; Varying the differential capacitance Inputting transimpedance amplifier and converting into voltage variation data And change the voltage data The method comprises the steps of superposing direct-current bias voltage to generate a baseband modulation signal, wherein the direct-current bias voltage is used for raising the signal level; generating a square wave carrier signal by a square wave carrier generating unit, modulating the baseband modulation signal and the square wave carrier signal, and generating a modulation signal; the modulation signal is synchronously demodulated through a ring diode demodulation circuit and two paths of signals are output, wherein the synchronous demodulation is in response to the phase switching of the square wave carrier signal, and demodulation is realized through periodically switching the transmission path and the polarity of the modulation signal; The two paths of signals are subjected to low-pass filtering so as to filter high-frequency carrier components and retain low-frequency acceleration signals; And carrying out differential operation on the two paths of signals after filtering, outputting a target voltage signal in linear relation with acceleration, and maintaining a target stable state of the scale factor under process deviation by maintaining constant gain conversion of the signal processing link.
2. The method of claim 1, wherein detecting the acceleration-induced capacitance change by the differential capacitance structure comprises: determining an initial capacitance of the differential capacitance structure based on the nominal plate spacing; Detecting a change in nominal plate spacing caused by acceleration-induced mass displacement; The capacitance change of the differential capacitance is calculated based on the change in the nominal plate spacing.
3. The method according to claim 2, wherein the method further comprises: The initial capacitance difference caused by the process variation is analyzed for evaluation of the process variation by detecting the null voltage without acceleration input.
4. The method of claim 1, wherein the differential capacitance variation Calculated by the following formula: Wherein, the Representing the displacement capacitance conversion coefficient, The displacement amount of the mass block is represented, Indicating the nominal plate spacing.
5. The method of claim 1, wherein the transimpedance amplifier's conversion factor is held constant for cancellation of process bias effects; The feedback resistor of the transimpedance amplifier is used for setting conversion gain, so that voltage change and capacitance change amount form a linear relation, and the conversion coefficient and the initial capacitance are decoupled.
6. The method of claim 1, wherein the voltage change data Calculated by the following formula: Wherein, the Representing the capacitive voltage conversion coefficient.
7. The method of claim 1, wherein said converting said voltage variation data Superimposed with the DC bias voltage and generating a baseband modulation signal, the baseband modulation signal is calculated by the following formula: Wherein, the A voltage value representing the baseband modulation signal; Representing the voltage variation data Adding value with DC bias voltage; indicating the dc bias voltage value.
8. The method of claim 1, wherein the generating the modulated signal is calculated based on: Wherein, the Representing the voltage value of the modulated signal; The frequency value of the square wave carrier signal is higher than the mechanical resonance frequency value of the accelerometer; Representing a square wave function.
9. The method of claim 1, wherein the ring diode demodulation circuit is a bridge structure formed by four diodes of a first diode, a second diode, a third diode and a fourth diode, and the step of synchronously demodulating the modulated signal and outputting two signals by the ring diode demodulation circuit comprises: The ring-based diode demodulation circuit is conducted by the first diode and the third diode in the positive half period of the square wave carrier wave, and the ring-based diode demodulation circuit is conducted by the second diode and the fourth diode in the negative half period of the square wave carrier wave.
10. A signal processing system for a capacitive accelerometer of a microelectromechanical system, comprising: The capacitance change acquisition module is used for detecting the capacitance change caused by acceleration through the differential capacitance structure to obtain differential capacitance change quantity ; A baseband modulation signal generation module for generating the differential capacitance variation Inputting transimpedance amplifier and converting into voltage variation data And change the voltage data The method comprises the steps of superposing direct-current bias voltage to generate a baseband modulation signal, wherein the direct-current bias voltage is used for raising the signal level; The modulating signal generating module is used for generating a square wave carrier signal by the square wave carrier generating unit, modulating the baseband modulating signal and the square wave carrier signal and generating a modulating signal; the two-way signal generation module is used for synchronously demodulating the modulation signal through the annular diode demodulation circuit and outputting two-way signals, wherein the synchronous demodulation is in response to the phase switching of the square wave carrier signal, and demodulation is realized by periodically switching the transmission path and the polarity of the modulation signal; The low-pass filtering module is used for carrying out low-pass filtering on the two paths of signals so as to filter out high-frequency carrier components and keep low-frequency acceleration signals; The target voltage signal generating module is used for carrying out differential operation on the two paths of signals after filtering, outputting a target voltage signal which has a linear relation with acceleration, and maintaining a target stable state of the scale factor under process deviation by maintaining constant gain conversion of the signal processing link.

Description

Signal processing method and system of micro-electromechanical system capacitive accelerometer Technical Field The application relates to the technical field of Micro-Electro-MECHANICAL SYSTEMS, MEMS (Micro-Electro-MECHANICAL SYSTEMS, MEMS), in particular to a signal processing method and a system of a capacitive accelerometer of a Micro-Electro-mechanical system. Background MEMS capacitive accelerometers measure acceleration by detecting differential capacitance changes caused by inertial mass displacement. The basic principle is that when acceleration acts on the mass block, the mass block generates displacement relative to the fixed electrode, so that the differential capacitance changes, and the acceleration value can be reversely deduced by detecting the capacitance change. However, during the fabrication of MEMS devices, variations in the etching process inevitably lead to deviations in critical dimension parameters from design. For example, a deviation of 20nm or more may occur due to a deviation of the plate pitch y from the design value y 0, a large difference between chips may occur due to the initial capacitance C 0, and the like. The prior art generally adopts three schemes, namely scheme one, a traditional C-V converting circuit adopts a switched capacitor circuit or a continuous time integrator to convert the capacitance change into voltage. The main problem with scheme one is that the conversion gain is highly dependent on the parasitic parameters of the reference capacitance and the op amp, and process variations can directly lead to gain variations, requiring piece-by-piece calibration. In the second scheme, a sinusoidal carrier is modulated and demodulated, and a signal is extracted by synchronous demodulation using a sinusoidal wave as a carrier. The scheme II has the advantages of mature theory, complex sine wave generator circuit, higher power consumption and strict design requirement of a phase-locked loop. Scheme three, sigma-Delta modulation (also known as Sigma-Delta modulation), employs over-sampling and noise shaping techniques. The third scheme has high precision, but has high circuit complexity and high requirement on digital circuit resources, and is not suitable for low-cost application. The scale factors of the prior art described above are significantly affected by process variations and the product consistency is poor, resulting in expensive individual calibration procedures that limit the large-scale application and cost advantages of the product. Accordingly, a solution to the above-described problems has arisen. Disclosure of Invention The application provides a signal processing method and a system of a capacitive accelerometer of a micro-electromechanical system, which are used for solving the defects in the prior art. According to a first aspect of an embodiment of the present application, there is provided a signal processing method of a capacitive accelerometer of a microelectromechanical system, including: detecting capacitance change caused by acceleration through a differential capacitance structure to obtain differential capacitance change quantity ; Varying the differential capacitanceInputting transimpedance amplifier and converting into voltage variation dataAnd change the voltage dataThe method comprises the steps of superposing direct-current bias voltage to generate a baseband modulation signal, wherein the direct-current bias voltage is used for raising the signal level; generating a square wave carrier signal by a square wave carrier generating unit, modulating the baseband modulation signal and the square wave carrier signal, and generating a modulation signal; the modulation signal is synchronously demodulated through a ring diode demodulation circuit and two paths of signals are output, wherein the synchronous demodulation is in response to the phase switching of the square wave carrier signal, and demodulation is realized through periodically switching the transmission path and the polarity of the modulation signal; The two paths of signals are subjected to low-pass filtering so as to filter high-frequency carrier components and retain low-frequency acceleration signals; And carrying out differential operation on the two paths of signals after filtering, outputting a target voltage signal in linear relation with acceleration, and maintaining a target stable state of the scale factor under process deviation by maintaining constant gain conversion of the signal processing link. In some embodiments, the detecting the acceleration-induced capacitance change by the differential capacitance structure includes: determining an initial capacitance of the differential capacitance structure based on the nominal plate spacing; Detecting a change in nominal plate spacing caused by acceleration-induced mass displacement; The capacitance change of the differential capacitance is calculated based on the change in the nominal plate spacing. In some embodiments, the m