Method and apparatus for driving a multi-oscillator system

Patent metadata

Field	Value
Publication number	US-10168194-B2
Application number	US-201514998168-A
Country	US
Kind code	B2
Filing date	Dec 24, 2015
Priority date	Dec 24, 2015
Publication date	Jan 1, 2019
Grant date	Jan 1, 2019

Abstract

Various embodiments mitigate the risk of frequency-lock in systems having multiple resonators by dynamically changing the frequency at which at least one of the resonators is driven. More particularly, the drive frequency of at least one of the resonators is changed often enough that the multiple resonators do not have time to achieve frequency lock. Changes in the oscillation of the resonators may be analyzed to determine, for example, acceleration of such systems. Some embodiments implement self-test by assessing expected performance of a system with toggling drive frequencies. More particularly, some embodiments implement self-test by artificially inducing displacement of a movable member of a system.

First claim

What is claimed is:

1. A method of detecting a physical quantity from a sensor, the sensor having a plurality of oscillation members including at least a first oscillation member and a second oscillation member, the method comprising:
driving the first oscillation member with a first drive signal having a first drive frequency in a first time interval and a second drive frequency in a second time interval;
driving the second oscillation member with a second drive signal;
receiving a first incoming signal representing an oscillation frequency of the first oscillation member;
receiving a second incoming signal representing an oscillation frequency of the second oscillation member; and
detecting the physical quantity based on the oscillation frequency of the first oscillation member and the oscillation frequency of the second oscillation member.

2. The method according to claim 1 , wherein the first incoming signal is obtained by passing an output of the first oscillation member through a first phase-locked loop and/or a first phase divider, and wherein the second incoming signal is obtained by passing an output of the second oscillation member through a second phase-locked loop and/or a second phase divider.

3. The method according to claim 1 , wherein the first drive frequency and the second drive frequency are different than a natural resonant frequency of the first oscillation member.

4. The method according to claim 1 , wherein the second drive signal has a third drive frequency in the first time interval and a fourth drive frequency in the second time interval.

5. The method according to claim 1 , wherein detecting the physical quantity comprises detecting an acceleration.

6. The method of claim 1 , wherein the first time interval and the second time interval are contiguous and have durations that are less than a frequency locking period between the first oscillation member and the second oscillation member.

7. A system for detecting a physical quantity, comprising:
an oscillation analyzer configured to:
drive a first oscillation member with a first drive signal having a first drive frequency in a first time interval and a second drive frequency in a second time interval;
drive a second oscillation member with a second drive signal;
receive a first incoming signal representing an oscillation frequency of the first oscillation member;
receive a second incoming signal representing an oscillation frequency of the second oscillation member; and
detect the physical quantity based on the oscillation frequency of the first oscillation member and the oscillation frequency of the second oscillation member.

8. The system of claim 7 , wherein the oscillation analyzer is configured to receive the first incoming signal at least in part by receiving an output of a first phase-locked loop coupled to the first oscillation member, and wherein the oscillation analyzer is configured to receive the second incoming signal at least in part by receiving an output of a second phase-locked loop coupled to the second oscillation member.

9. The system of claim 8 , wherein the first drive frequency and the second drive frequency are different than a natural resonant frequency of the first oscillation member.

10. The system of claim 7 , wherein the oscillation analyzer is configured to receive the first incoming signal at least in part by receiving an output of a first phase divider coupled to the first oscillation member and wherein the oscillation analyzer is configured to receive the second incoming signal at least in part by receiving an output of a second phase divider coupled to the second oscillation member.

11. The system of claim 7 , wherein the oscillation analyzer comprises:
a first counter configured to produce a first frequency count based on the first incoming signal;
a second counter configured to produce a second frequency count based on the second incoming signal; and
a first subtractor configured to subtract the first frequency count from the second frequency count to produce a frequency difference count.

12. The system of claim 7 , wherein the second drive signal has a third drive frequency in the first time interval and a fourth drive frequency in the second time interval.

13. The system of claim 12 , wherein the third drive frequency and the fourth drive frequency are different than a natural resonant frequency of the second oscillation member.

14. The system of claim 7 , wherein the first time interval and the second time interval are contiguous and have durations that are less than a frequency locking period between the first oscillation member and the second oscillation member.

15. A method of testing a system having a plurality of movable members, the method comprising:
driving a first member with a first member drive signal, and toggling the first member drive signal between a first drive frequency and a second drive frequency;
driving a second member with a second member drive signal, and toggling the second member drive signal between a third drive frequency and a fourth drive frequency; and
determining whether the first and second members are oscillating at target frequencies.

16. The method of testing a system of claim 15 , wherein determining whether the first and second members are oscillating at target frequencies comprises:
determining a first member oscillating frequency delta based on a difference between a frequency of oscillation of the first member when driven at the first drive frequency and a frequency of oscillation of the first member when driven at the second drive frequency;
determining a second member oscillating frequency delta based on a difference between a frequency of oscillation of the second member when driven at the third drive frequency and a frequency of oscillation of the second member when driven at the fourth frequency; and
comparing the first member oscillating frequency delta and the second member oscillating frequency delta.

17. The method of testing a system of claim 16 , wherein determining a first member oscillating frequency delta comprises:
filtering a signal representing a difference in oscillation frequency between the first member and the second member to produce first member self-test data and second member self-test data;
comparing the first member self-test data and second member self-test data to a target value; and
indicating a malfunction in the system if comparison is not equal to the target value.

18. The method of testing a system of claim 16 , further comprising at least one of: terminating operation of the system if a malfunction is indicated; or inducing a known displacement of at least one of the plurality of movable members and assessing whether the system produces an output accurately reporting an acceleration equal to an acceleration that would cause the known displacement of the at least one of the plurality of movable members.

19. The method of testing a system of claim 15 , wherein the first and second movable members comprise at least one of an oscillator or a frame.

20. A method of operating a sensor for detecting acceleration, the sensor having a plurality of oscillation members including at least a first oscillation member and a second oscillation member, the method comprising:
driving the first oscillation member with a first drive signal having a first drive frequency in a first time interval and a second drive frequency in a second time interval;
driving the second oscillation member with a second drive signal;
receiving

Assignees

• Analog Devices Inc

Inventors

• Vohra Gaurav
• Clark William A
• Motiee Mehrnaz

Classifications

• G01D21/00 Primary

  Measuring or testing not otherwise provided for · CPC title

• H03L7/18

  using a frequency divider or counter in the loop (H03L7/20, H03L7/22 take precedence) · CPC title

• H03L7/141

  the phase-locked loop controlling several oscillators in turn · CPC title

• G01D18/00

  Testing or calibrating apparatus or arrangements provided for in groups G01D1/00 - G01D15/00 · CPC title

• H03L7/00

  Automatic control of frequency or phase; Synchronisation · CPC title