METHODS AND APPARATUS FOR TUNING DEVICES HAVING MECHANICAL RESONATORS

• US 20100308927A1
• Filed: 02/03/2010
• Published: 12/09/2010
• Est. Priority Date: 02/04/2009
• Status: Active Grant

• Current Assignee: Analog Devices, Inc.
• Original Assignee: Sand9, Inc.
• Inventors: Rebel, Reimund, Schoepf, Klaus Juergen
• Granted Patent: US 8,319,566 B2
• Time in Patent Office: Days
• US Class Current: 331/1R
• CPC Class Codes: H03B 5/30 with frequency-determining element being electromechanical resonator
• CPC Class Codes: H03H 2009/02204 operating on an additional circuit element, e.g. applying a tuning DC voltage to a passive circuit element connected to the resonator
• CPC Class Codes: H03H 9/17 having a single resonator crystal tuning forks H03H9/21
• CPC Class Codes: H03H 9/2426 in combination with other electronic elements
• CPC Class Codes: H03H 9/25 Constructional features of resonators using surface acoustic waves devices for manipulating acoustic surface waves in general G10K11/36
• CPC Class Codes: H03L 7/00 Automatic control of frequency or phase; Synchronisation

Abstract

Methods and apparatus for tuning devices having mechanical resonators are described. In one implementation, a mechanical resonator and a phase shifter are configured in a feedback loop, so that the phase shifter shifts the phase of the resonator output signal. The amount of phase shift induced by the phase shifter may be variable. In another implementation, an LC tuning subcircuit is coupled to a mechanical resonator. In some implementations, the LC tuning subcircuit has a variable capacitance. One or more of the apparatus described herein may be implemented as part, or all, of a microelectromechanical system (MEMS).

Claims

1. A method of tuning a device having a mechanical resonator, the method comprising:

producing an output signal of the mechanical resonator;

shifting a phase of the output signal of the mechanical resonator to produce a phase-shifted signal having a different phase than the phase of the output signal of the mechanical resonator; and

providing the phase-shifted signal to the mechanical resonator.

2. The method of claim 1, wherein shifting the phase of the output signal of the mechanical resonator comprises inverting the output signal of the mechanical resonator.

3. The method of claim 1, wherein shifting the phase of the output signal of the mechanical resonator comprises performing a coarse phase adjustment and a fine phase adjustment.

4. The method of claim 3, wherein performing the coarse phase adjustment comprises inverting the output signal of the mechanical resonator.

5. The method of claim 3, wherein the coarse phase adjustment is performed prior to the fine phase adjustment.

6. The method of claim 5, wherein performing the coarse phase adjustment comprises inverting the output signal of the mechanical resonator.

7. The method of claim 3, wherein the fine phase adjustment is performed prior to the coarse phase adjustment.

8. The method of claim 1, further comprising amplifying the output signal of the mechanical resonator prior to shifting the phase of the output signal of the mechanical resonator.

9. The method of claim 1, further comprising amplifying the phase-shifted signal.

10. The method of claim 1, wherein the mechanical resonator has a resonance frequency that varies with temperature, and wherein shifting the phase of the output signal of the mechanical resonator comprises shifting the phase to compensate for a temperature-induced shift in the resonance frequency of the mechanical resonator.

11. The method of claim 1, wherein the mechanical resonator has a variable resonance frequency, and wherein shifting the phase of the output signal of the mechanical resonator comprises shifting the phase to compensate for variations in the resonance frequency of the mechanical resonator.

12. The method of claim 11, wherein the variable resonance frequency varies in response to variations in ambient pressure.

13. The method of claim 11, wherein the mechanical resonator is contained at least partially within a package, and wherein the variable resonance frequency varies in response to variations in package-induced stress.

14. The method of claim 11, wherein the mechanical resonator is formed of two or more materials, and wherein the variable resonance frequency varies in response to material-dependent stress.

15. The method of claim 1, further comprising performing stress tuning of the device using electrostatic or piezoelectric techniques.

16. The method of claim 1, wherein the output signal comprises multiple ends having approximately equal phases.

17. The method of claim 16, wherein shifting the phase of the output signal comprises shifting the phases of the ends of the output signal by an approximately equal amount.

18. The method of claim 16, wherein shifting the phase of the output signal comprises shifting a phase of a first end of the output signal by a first amount and shifting a phase of a second end of the output signal by a second amount different than the first amount.

19. The method of claim 18, wherein the first amount and the second amount differ by between approximately 1-10 degrees.

20. A device, comprising:

a mechanical resonator; and

a phase shifter,

wherein the mechanical resonator and the phase shifter are configured in a feedback loop.

21. The device of claim 20, wherein the phase shifter comprises an inverting amplifier.

22. The device of claim 20, wherein the mechanical resonator is at least part of a microelectromechanical system (MEMS).

23. The device of claim 20, wherein the phase shifter is a variable phase shifter.

24. The device of claim 20, wherein the phase shifter comprises a coarse phase adjustment subcircuit and a fine phase adjustment subcircuit.

25. A method of tuning a device having a mechanical resonator, the method comprising:

producing a multi-ended output signal of the mechanical resonator, the multi-ended output signal comprising a first end and a second end;

producing a phase-shifted signal by phase shifting at least one of the first end and the second end; and

providing the phase-shifted signal as an input signal to the mechanical resonator.

26. The method of claim 25, wherein producing the phase-shifted signal comprises phase shifting the first end by a first amount and phase shifting the second end by a second amount.

27. The method of claim 26, wherein the first amount and the second amount differ from each other.

28. The method of claim 26, wherein the first amount and the second amount are variable.

29. The method of claim 26, which the first amount and the second amount differ from each by between approximately 1-20 degrees.

30. The method of claim 26, wherein the first amount is within approximately 5 degrees of the second amount.

31. The method of claim 26, wherein phase shifting the first end of the output signal by a first amount and phase shifting the second end of the output signal by a second amount is performed to maintain an approximately constant power of the phase-shifted signal over time.

32. The method of claim 25, wherein the multi-ended output signal of the mechanical resonator is a differential signal.

33. A method of tuning a mechanical resonator of an oscillating circuit, the method comprising:

producing an output signal of the mechanical resonator comprising a first end and a second end;

amplifying and phase shifting the first end and second end by different amounts to produce a modified signal; and

inputting the modified signal to the mechanical resonator.

34. The method of claim 33, wherein amplifying the first end and second end by different amounts comprises amplifying only one of the first end and the second end.

35. The method of claim 33, wherein phase shifting the first end and second end by different amounts comprises phase shifting only one of the first end and the second end.