MEMS QUADRATURE CANCELLATION AND SIGNAL DEMODULATION

• US 20130269413A1
• Filed: 04/11/2013
• Published: 10/17/2013
• Est. Priority Date: 04/12/2012
• Status: Active Grant

• Current Assignee: Semiconductor Components Industries LLC (ON Semiconductor Corporation)
• Original Assignee: Fairchild Semiconductor Corporation (ON Semiconductor Corporation)
• Inventors: Tao, Hai, Opris, Ion
• Granted Patent: US 9,625,272 B2
• Time in Patent Office: Days
• US Class Current: 73/1.38
• CPC Class Codes: B81B 7/008 MEMS characterised by an electronic circuit specially adapted for controlling or driving the same B81B7/0087 takes precedence; arrangements for starting, regulating, braking, or otherwise controlling an actuator H02N; control arrangements or circuits for visual indicators G09G3/00
• CPC Class Codes: B81B 7/02 containing distinct electrical or optical devices of particular relevance for their function, e.g. microelectro-mechanical systems [MEMS] B81B7/04 takes precedence
• CPC Class Codes: G01C 19/5776 Signal processing not specific to any of the devices covered by groups G01C19/5607 - G01C19/5719
• CPC Class Codes: G01C 25/00 Manufacturing, calibrating, cleaning, or repairing instruments or devices referred to in the other groups of this subclass testing, calibrating or compensating compasses G01C17/38
• CPC Class Codes: G01P 15/097 by vibratory elements

Abstract

In certain examples, a quadrature cancellation apparatus can include a drive charge amplifier configured to couple to a proof mass of a MEMS device and to provide oscillation motion information, a first sense charge amplifier configured to couple to the proof mass and to provide first sense information of a first movement of the MEMS device, a first programmable amplifier configured to receive the oscillation motion information and provide amplified oscillation motion information, a first summer configured to cancel quadrature error of the first sense information using the first sense information and the amplified oscillation motion information to provide quadrature-corrected first sense information, a phase shifter configured to receive the oscillation motion information and to provide carrier information, and a first multiplier configured to provide demodulated first sense information using the quadrature-corrected first sense information and the carrier information.

Claims

1. A quadrature cancellation apparatus comprising:

a drive charge amplifier configured to couple to a proof mass of a MEMS device and to provide oscillation motion information;

a first sense charge amplifier configured to couple to the proof mass and to provide first sense information of a first movement of the MEMS device;

a first programmable amplifier configured to receive the oscillation motion information and provide amplified oscillation motion information;

a first summer configured to cancel quadrature error of the first sense information using the first sense information and the amplified oscillation motion information to provide quadrature-corrected first sense information;

a phase shifter configured to receive the oscillation motion information and to provide carrier information; and

a first multiplier configured to provide demodulated first sense information using the quadrature-corrected first sense information and the carrier information.

2. The apparatus of claim 1, including a first baseband buffer configured to receive the demodulated first sense information and to provide buffered first sense information.

3. The apparatus of claim 1, wherein a first switch matrix includes the first summer and the first multiplier.

4. The apparatus of claim 1, wherein the drive charge amplifier and the first sense charge amplifier include delay-matched amplifiers.

5. The apparatus of claim 1, wherein the phase shifter is programmable to provide about 90 degrees of phase shift in a first state and about zero degrees of phase shift in a second, calibration state.

6. The apparatus of claim 1, including:

a second sense charge amplifier configured to couple to the proof mass and to provide second sense information of a second movement of the MEMS device;

a second programmable amplifier configured to receive the oscillation motion information and provide amplified oscillation motion information;

a second summer configured to cancel quadrature error of the second sense information using the second sense information and the amplified oscillation motion information to provide quadrature-corrected second sense information; and

a second multiplier configured to provide demodulated second sense information using the quadrature-corrected second sense information and the carrier information.

7. The apparatus of claim 6, including a second baseband buffer configured to receive the demodulated second sense information and to provide buffered second sense information.

8. The apparatus of claim 6, wherein a second switch matrix includes the second summer and the second multiplier.

9. The apparatus of claim 6, wherein the drive charge amplifier and the second sense charge amplifier include delay-matched amplifiers.

10. A method for canceling quadrature error of a MEMS device signal, the method comprising:

providing oscillation motion information using a drive charge amplifier coupled to a proof mass of a MEMS device;

providing first sense information using a first sense charge amplifier coupled to the proof mass, the first sense information corresponding to a first movement of the MEMS device;

providing amplified oscillation motion information using a first programmable amplifier and the oscillation motion information;

canceling first quadrature error of the first sense information using a first summer and the amplified oscillation motion information to provide quadrature-corrected first sense information;

shifting a phase of the oscillation motion information using a phase shifter to provide carrier information; and

demodulating the quadrature-corrected first sense information using a first multiplier, the quadrature-corrected first sense information, and the carrier information to provide demodulated first sense information.

11. The method of claim 10, including buffering the demodulated first sense information using a first baseband buffer to provide buffered first sense information.

12. The method of claim 10, wherein the canceling first quadrature error of the first sense information using a first summer and the demodulating the quadrature-corrected first sense information using a first multiplier includes using a first switch matrix including the first summer and the first multiplier.

13. The method of claim 10, wherein the providing oscillation motion information using a drive charge amplifier coupled to a proof mass of a MEMS device and the providing first sense information using a first sense charge amplifier coupled to the proof mass includes using a drive charge amplifier and a first sense charge amplifier that are delay-matched to each other.

14. The method of claim 10, wherein shifting a phase of the oscillation motion information using a phase shifter to provide carrier information includes shifting a phase of the oscillation motion information 90 degrees using a first state of the phase shifter to provide the carrier information.

15. The method of claim 10, including shifting a phase of the oscillation motion information zero degrees using a second state of the phase shifter to calibrate a gain of the first programmable amplifier.

16. A MEMS system comprising:

a MEMS gyroscope having a proof mass;

a quadrature cancellation circuit configured to provide movement information of the MEMS gyroscope, the quadrature cancellation including;

a drive charge amplifier configured to couple to the proof mass and to provide oscillation motion information;

a first sense charge amplifier configured to couple to the proof mass and to provide first sense information of a first movement of the MEMS device;

a first programmable amplifier configured to receive the oscillation motion information and provide amplified oscillation motion information;

a first summer configured to cancel quadrature error of the first sense information using the first sense information and the amplified oscillation motion information to provide quadrature-corrected first sense information;

a phase shifter configured to receive the oscillation motion information and to provide carrier information; and

a first multiplier configured to provide demodulated first sense information using the quadrature-corrected first sense information and the carrier information.

17. The system of claim 16, including a first baseband buffer configured to receive the demodulated first sense information and to provide buffered first sense information, wherein the movement information includes the buffered first sense information.

18. The system of claim 17, wherein the quadrature cancellation circuit includes:

a second sense charge amplifier configured to couple to the proof mass and to provide second sense information of a second movement of the MEMS device;

a second programmable amplifier configured to receive the oscillation motion information and provide amplified oscillation motion information;

a second summer configured to cancel quadrature error of the second sense information using the second sense information and the amplified oscillation motion information to provide quadrature-corrected second sense information;

a second multiplier configured to provide demodulated second sense information using the quadrature-corrected second sense information and the carrier information; and

a second baseband buffer configured to receive the demodulated second sense information and to provide buffered second sense information, wherein the movement information includes the buffered second sense information, and wherein the first movement and the second movement are not parallel to each other.

19. The system of claim 16, wherein a first switch matrix includes the first summer and the first multiplier.

20. The system of claim 16, wherein the drive charge amplifier and the first sense charge amplifier include delay-matched amplifiers.