# US 12,601,593 B2 · Auto-calibration method for inertial MEMS sensors > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,601,593 B2 - Document ID: US12601593B2 - Status: Granted - Kind: B2 - Application number: 18/240,955 - Filed: 2023-08-31 - Published: 2025-03-06 - Granted: 2026-04-14 - Earliest claimed: 2023-08-31 - Assignees: STMicroelectronics International N.V. - Applicants: STMicroelectronics International N.V. - Inventors: Alessandro Magnani; Matteo Quartiroli; Alessandro Mecchia - Web page: https://patentgrep.com/patent/US12601593B2 ## CPC - G01C 19/5712: the devices involving a micromechanical structure - G01C 19/5776: Signal processing not specific to any of the devices covered by groups G01C19/5607 - G01C19/5719 - G01C 25/005: {initial alignment, calibration or starting-up of inertial devices} - G01C: MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY (measuring liquid level G01F; radio navigation, determining distance or velocity by use of propagation effects, e.g. Doppler effects, propagation time, of radio waves, analogous arrangements using other waves G01S) ## Abstract A sensor module includes a pattern generator configured to generate a variable frequency self-test signal. The sensor module includes an inertial sensor including a self-test electrode configured to receive the frequency sweep self-test signal. The inertial sensor is configured to generate an analog sensor signal based on the self-test signal. The sensor module includes an analog to digital converter configured to generate a digital sensor signal based on the analog sensor signal and a demodulator including a first input configured to receive the digital sensor signal, a second input configured to receive the self-test signal, and an output configured to output a demodulated signal. The sensor module includes a first low pass filter coupled to the output of the demodulator and configured to generate a baseband signal. The sensor module includes a calibration circuit configured to identify different MEMS characteristics, like resonance frequency, Q-factor, or sensitivity based on the baseband signal. ## Claims ### Claim 1 A method, comprising: generating, with an inertial sensor, an analog sensor signal by applying a self-test signal to a self-test electrode of an inertial sensor; converting the analog sensor signal to a digital sensor signal; generating, with a first demodulator, a demodulated signal by passing the self-test signal and the digital sensor signal to a first demodulator; generating a baseband signal by passing the first demodulated signal through a low pass filter; identifying, with a calibration circuit, a zero-crossing frequency and a first peak frequency in the baseband signal; and calibrating the inertial sensor based on the zero-crossing frequency and the first peak frequency. ### Claim 2 (depends on 1) The method of claim 1, wherein calibrating the inertial sensor includes calibrating a digital notch filter based on the zero-crossing frequency and the first peak frequency. ### Claim 3 (depends on 1) The method of claim 1, comprising calculating a Q factor of the inertial sensor based on the first peak frequency and the zero-crossing frequency. ### Claim 4 (depends on 1) The method of claim 1, wherein the zero-crossing frequency is a resonant frequency of the inertial sensor. ### Claim 5 (depends on 1) The method of claim 1, comprising identifying, with the calibration circuit, a second peak frequency I the baseband signal, wherein the first peak frequency is a positive peak frequency, the second peak frequency is a negative peak frequency, and the zero-crossing frequency is between the first peak frequency and the second peak frequency. ### Claim 6 (depends on 5) The method of claim 5, wherein the inertial sensor is a gyroscope, the method comprising calculating a Q factor of the inertial sensor based on the first peak frequency, the second peak frequency, and the zero-crossing frequency. ### Claim 7 (depends on 6) The method of claim 6, comprising calculating the Q factor based on a drive frequency of the inertial sensor. ### Claim 8 (depends on 1) The method of claim 1, comprising passing the self-test signal to the self-test electrode via a first variable delay element. ### Claim 9 (depends on 8) The method of claim 8, comprising passing the self-test signal to the demodulator via a second variable delay element. ### Claim 10 (depends on 9) The method of claim 9, wherein calibrating the inertial sensor includes adjusting at least one of the first and the second variable delay element. ### Claim 11 (depends on 1) The method of claim 1, wherein the self-test signal is frequency sweep signal. ### Claim 12 (depends on 1) The method of claim 1, wherein the self-test signal is a variable frequency self-test signal. ### Claim 13 A method, comprising: applying a frequency sweep self-test signal to a test electrode of an inertial sensor and to a first demodulator of the inertial sensor; generating a first digital signal with the inertial sensor based on the frequency sweep self-test signal; generating a demodulated signal by demodulating the first digital signal and the frequency sweep self-test signal; generating a baseband signal by passing the demodulated signal through a digital low-pass filter; and identifying a resonant frequency of the inertial sensor by analyzing the baseband signal with a calibration circuit. ### Claim 14 (depends on 13) The method of claim 13, wherein identifying the resonant frequency includes identifying a zero-crossing frequency of the baseband signal. ### Claim 15 (depends on 14) The method of claim 14, comprising: identifying, with the calibration circuit, a first peak frequency of the baseband signal; and calculating a Q factor of the inertial sensor based on the resonant frequency and the first peak frequency. ### Claim 16 (depends on 14) The method of claim 14, comprising: identifying, with the calibration circuit, a positive frequency of the baseband signal; identifying, with the calibration circuit, a negative frequency of the baseband signal; and calculating a Q factor of the inertial sensor based on the resonant frequency, the positive peak frequency, and the negative peak frequency. ### Claim 17 A device comprising: a pattern generator configured to generate a variable frequency self-test signal; an inertial sensor including a self-test electrode configured to receive the variable frequency self-test signal, the inertial sensor configured to generate an analog sensor signal based on the variable frequency self-test signal; an analog to digital converter configured to generate a digital sensor signal based on the analog sensor signal; a demodulator including a first input configured to receive the digital sensor signal, a second input configured to receive the self-test signal, and an output configured to output a demodulated signal; a first low pass filter coupled to the output of the demodulator and configured to generate a baseband signal; and a calibration circuit configured to identify a resonant frequency of the inertial sensor by analyzing the baseband signal. ### Claim 18 (depends on 17) The device of claim 17, wherein the calibration circuit is configured to identify the resonant frequency as a zero-crossing frequency of the baseband signal. ### Claim 19 (depends on 18) The device of claim 18, wherein the calibration circuit is configured to identify a first peak frequency of the baseband signal and to calculate a Q factor of the inertial sensor based on the resonant frequency and the first peak frequency. ### Claim 20 (depends on 19) The device of claim 19, wherein the calibration circuit is configured to identify a positive frequency of the baseband signal, to identify a negative frequency of the baseband signal, and to calculate a Q factor of the inertial sensor based on the resonant frequency, the positive peak frequency, and the negative peak frequency. ### Claim 21 (depends on 17) The device of claim 17, wherein the variable frequency self-test signal includes pseudo random sequences.