Control circuit of a MEMS gyroscope, MEMS gyroscope and control method

Patent metadata

Field	Value
Publication number	US-12305986-B2
Application number	US-202217899478-A
Country	US
Kind code	B2
Filing date	Aug 30, 2022
Priority date	Sep 27, 2021
Publication date	May 20, 2025
Grant date	May 20, 2025

Abstract

The control circuit for a MEMS gyroscope is configured to receive a measurement signal which has a quadrature component and a sensing component. The control circuit has: an input stage which acquires an input signal, generating an acquisition signal, where the input signal is a function of the measurement signal and of a quadrature cancellation signal; a processing stage which extracts a first component of the acquisition signal, indicative of the sensing component of the measurement signal and having a sensing frequency band; and a quadrature correction stage which extracts a second component of the acquisition signal, indicative of the quadrature component of the measurement signal, and generates the quadrature cancellation signal from a reference signal. The quadrature cancellation signal is a signal modulated as a function of the second component of the acquisition signal, at an update frequency which is outside the sensing frequency band.

First claim

The invention claimed is:

1. A control circuit for a MEMS gyroscope, configured to receive a measurement signal having a quadrature component and a sensing component from the MEMS gyroscope, the control circuit comprising:
an input stage configured to acquire an input signal and to generate an acquisition signal in response to the input signal, the input signal being a function of the measurement signal and of a quadrature cancellation signal;
a processing stage configured to obtain a first component of the acquisition signal, the first component of the acquisition signal being indicative of the sensing component of the measurement signal and having a sensing frequency band; and
a quadrature correction stage configured to extract a second component of the acquisition signal and to generate the quadrature cancellation signal based on a reference signal, the second component of the acquisition signal being indicative of the quadrature component of the measurement signal,
wherein the quadrature cancellation signal is a signal modulated as a function of the second component of the acquisition signal, at an update frequency which is outside the sensing frequency band.

2. The control circuit according to claim 1 , wherein the quadrature correction stage is a sigma-delta modulator.

3. The control circuit according to claim 1 , wherein the quadrature correction stage comprises:
a filtering stage configured to filter the second component of the acquisition signal to generate a filtered signal;
a quantizer configured to receive an update clock signal having the update frequency and to generate, based on the filtered signal, a digital correction signal having a data rate equal to the update frequency; and
a modulator configured to modulate one or more of an amplitude or a phase of the quadrature cancellation signal based on the digital correction signal.

4. The control circuit according to claim 3 , wherein the input stage has an input node configured to receive the measurement signal, and
wherein the modulator comprises a first variable capacitor having a first terminal coupled to the input node of the input stage and a second terminal configured to receive an input voltage that is a function of the reference signal, the digital correction signal being configured to modify the capacitance of the first variable capacitor to modulate the amplitude of the quadrature cancellation signal.

5. The control circuit according to claim 3 , wherein the digital correction signal comprises a sign signal indicative of a phase-shift sign of the filtered signal, and
wherein the modulator further comprises a phase-shift block configured to invert the phase of the quadrature cancellation signal as a function of the sign signal.

6. The control circuit according to claim 3 , wherein the update clock signal is synchronized with zero crossings of the reference signal.

7. The control circuit according to claim 1 , wherein the reference signal has a first frequency and the update frequency is equal to about two times the first frequency.

8. The control circuit according to claim 1 , configured to receive the reference signal from an oscillating system of the MEMS gyroscope,
wherein the control circuit further comprises a driving module configured to generate a driving signal having a first frequency and configured to cause a driving oscillation of the oscillating system, the reference signal being indicative of a driving oscillation of the oscillating system.

9. The control circuit according to claim 8 , wherein the driving module is configured to generate a first demodulating signal having the first frequency and in quadrature with respect to the reference signal, a second demodulating signal having the first frequency and in-phase with respect to the reference signal, the processing stage being configured to extract the first component of the acquisition signal using the first demodulating signal, the quadrature correction stage being configured to extract the second component of the acquisition signal using the second demodulating signal.

10. The control circuit according to claim 4 , wherein the modulator further comprises a second variable capacitor and a register, the second variable capacitor having a first terminal coupled to the input node of the input stage and a second terminal configured to receive a second input voltage that is a function of the reference signal, the register being configured to generate a calibration correction signal, the calibration correction signal being configured to set a calibration capacitance value of the second variable capacitor.

11. The control circuit according to claim 1 , having a differential architecture, wherein the input stage has a first input and a second input and is configured to receive a measurement signal of differential type from the MEMS gyroscope and a quadrature cancellation signal of differential type from the quadrature correction stage.

12. A control method for a MEMS gyroscope comprising a control circuit, the control method comprising, by the control circuit:
receiving a measurement signal having a quadrature component and a sensing component from the MEMS gyroscope;
acquiring an input signal, the input signal being a function of the measurement signal and of a quadrature cancellation signal;
generating an acquisition signal in response to the acquisition of the input signal;
extracting a first component of the acquisition signal indicative of the sensing component of the measurement signal, the first component of the acquisition signal having a sensing frequency band;
extracting a second component of the acquisition signal indicative of the quadrature component of the measurement signal; and
generating the quadrature cancellation signal from a reference signal,
wherein the quadrature cancellation signal is a signal modulated based on the second component of the acquisition signal, at an update frequency which is outside the sensing frequency band.

13. The control method according to claim 12 , wherein generating the quadrature cancellation signal comprises:
filtering the second component of the acquisition signal to generate a filtered signal;
generating, from the filtered signal and by a quantizer controlled by an update clock signal having the update frequency, a digital correction signal having a data rate equal to the update frequency; and
modulating one or more of an amplitude lor a phase of the quadrature cancellation signal based on the digital correction signal, the quadrature cancellation signal configured to cancel the quadrature component of the measurement signal in the input signal.

14. The control method according to claim 13 , wherein the update clock signal is synchronized with zero crossings of the reference signal.

15. A MEMS gyroscope having a control circuit and an oscillating system, the control circuit comprising:
a quadrature correction stage configured to generate a quadrature cancellation signal based on a reference signal and a quadrature component of a measurement signal of the oscillating system, the quadrature cancellation signal configured to cancel the quadrature component of the measurement signal,
wherein the quadrature correction stage includes a first phase shifter and a first variable capacitor, the first variable capacitor coupled to an output of the first phase shifter and configured to vary a capacitance value of the first variable capacitor based on the calibration correction signal.

16. The MEMS gyroscope of claim 15 , wherein the quadrature correction stage includes a second phase shifter configured to m

Assignees

• St Microelectronics Srl

Inventors

• Granata Angelo

Classifications

• H03M3/40

  Arrangements for handling quadrature signals, e.g. complex modulators · CPC title

• H03M3/344

  by filtering other than the noise-shaping inherent to delta-sigma modulators, e.g. anti-aliasing · CPC title

• G01C19/5776 Primary

  Signal processing not specific to any of the devices covered by groups G01C19/5607 - G01C19/5719 · CPC title

• G01C19/5712 Primary

  the devices involving a micromechanical structure · CPC title