METHODS AND APPARATUS FOR TUNING DEVICES HAVING RESONATORS

• US 20100315170A1
• Filed: 07/02/2010
• Published: 12/16/2010
• Est. Priority Date: 02/04/2009
• Status: Active Grant

• Current Assignee: Analog Devices, Inc.
• Original Assignee: Sand9, Inc.
• Inventors: Locascio, David, Kuypers, Jan H., Rebel, Reimund
• Granted Patent: US 8,456,250 B2
• Time in Patent Office: Days
• US Class Current: 331/15
• CPC Class Codes: H03B 5/30 with frequency-determining element being electromechanical resonator
• CPC Class Codes: H03B 5/326 the resonator being an acoustic wave device, e.g. SAW or BAW device
• 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 resonators are described. Phase shifters are included in the circuits and used to shift the phase of the output signal(s) of the resonators. In some implementations, the phase shifters are configured in a feedback loop with the resonators. 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:

receiving an output signal of the mechanical resonator;

producing a phase-shifted signal from the output signal; and

inputting the phase-shifted signal to the mechanical resonator.

2. The method of claim 1, wherein producing the phase-shifted signal is performed without using a variable capacitor.

3. The method of claim 2, wherein producing the phase-shifted signal is performed without using a varactor.

4. The method of claim 2, wherein producing the phase-shifted signal is performed without using an inductor.

5. The method of claim 1, wherein producing the phase-shifted signal comprises generating, from the output signal, a first signal and a second signal and phase shifting the first signal relative to the second signal.

6. The method of claim 5, wherein producing the phase-shifted signal further comprises amplitude weighting the first signal and second signal by different amounts.

7. The method of claim 6, wherein producing the phase-shifted signal further comprises combining the first signal and second signal subsequent to phase-shifting the first signal relative to the second signal and amplitude weighting the first signal and second signal by different amounts.

8. The method of claim 7, wherein combining the first signal and the second signal comprises adding the first signal and the second signal together.

9. The method of claim 7, wherein producing the phase-shifted signal further comprises limiting an amplitude of at least one of the first signal and the second signal.

10. The method of claim 9, wherein limiting an amplitude of at least one of the first signal and the second signal comprises limiting the amplitude by an amount configured to provide a feedback loop comprising the mechanical resonator with unity gain.

11. The method of claim 6, wherein amplitude weighting the first signal and second signal by different amounts comprises applying unity gain to one of the first signal and second signal.

12. The method of claim 5, wherein phase-shifting the first signal relative to the second signal comprises phase shifting only one of the first signal and second signal.

13. The method of claim 5, wherein generating the first signal and the second signal comprises splitting the output signal.

14. The method of claim 1, wherein the output signal of the mechanical resonator is a multi-ended signal comprising a first end and a second end and wherein producing the phase-shifted signal comprises phase-shifting the first end relative to the second end.

15. The method of claim 14, wherein phase-shifting the first end relative to the second end comprises phase-shifting the first end by a first amount and phase shifting the second end by a second amount.

16. The method of claim 14, wherein producing the phase-shifted signal further comprises amplitude weighting the first end and second end by different amounts.

17. The method of claim 16, wherein phase-shifting the first end relative to the second end is performed prior to amplitude weighting the first end and second end by different amounts.

18. The method of claim 16, wherein amplitude weighting the first end and second end by different amounts is performed prior to phase-shifting the first end relative to the second end.

19. The method of claim 16, wherein producing the output signal further comprises limiting an amplitude of at least one of the first end and the second end.

20. The method of claim 14, wherein producing the phase-shifted signal further comprises adding signals resulting from phase-shifting the first end relative to the second end using a differential summation circuit.

21. A device, comprising:

a mechanical resonator; and

a processing circuit coupled to the mechanical resonator and configured to receive an output signal of the mechanical resonator, produce a phase-shifted signal shifted in phase relative to the output signal, and provide the phase-shifted signal to an input of the mechanical resonator.

22. The device of claim 21, wherein the phase-shifted signal has a variable amount of phase shift, and wherein the processing circuit does not include a variable capacitor.

23. The device of claim 22, wherein the processing circuit does not include a varactor.

24. The device of claim 22, wherein the processing circuit does not include an inductor.

25. The device of claim 21, wherein the processing circuit comprises a phase shifter configured to generate, from the output signal, a first signal and a second signal and phase shift the first signal relative to the second signal.

26. The device of claim 25, wherein the processing circuit further comprises a gain circuit coupled to the phase shifter and configured to modify an amplitude of the first signal by a different amount than an amplitude of the second signal.

27. The device of claim 26, wherein the processing circuit further comprises a combination circuit configured to combine the first signal and second signal subsequent to operation of the phase shifter and gain circuit.

28. The device of claim 27, wherein the combination circuit is a summation circuit.

29. The device of claim 27, wherein the processing circuit further comprises a limiter configured to limit an amplitude of at least one of the first signal and the second signal.

30. The device of claim 29, wherein the limiter is configured to limit the amplitude by an amount configured to provide a feedback loop comprising the mechanical resonator with unity gain.

31. The device of claim 26, wherein the gain stage is configured to apply unity gain to one of the first signal and second signal.

32. The device of claim 25, wherein the phase shifter is configured to shift only one of the first signal and second signal.

33. The device of claim 25, wherein the phase shifter is configured to generate, at least in part, the first signal and second signal by splitting the output signal.

34. The device of claim 21, wherein the phase shifter is a variable phase shifter configured to provide a variable amount of phase shift of the output signal of the mechanical resonator.

35. A device, comprising:

a differential mechanical resonator configured to produce a differential output signal; and

a processing circuit coupled to the differential mechanical resonator and configured to receive the differential output signal, generate a phase-shifted differential signal, and provide the phase-shifted differential signal to a differential input of the differential mechanical resonator.

36. The device of claim 35, wherein the differential output signal comprises a first end and a second end, and wherein the processing circuit comprises a phase shifter configured to shift a phase of at least one of the first end and the second end.

37. The device of claim 36, wherein the phase shifter is configured to shift a phase of the first end by a first amount and shift a phase of the second end by a second amount.

38. The device of claim 37, wherein the phase shifter comprises a first phase shifter configured to shift the phase of the first end by the first amount and a second phase shifter configured to shift the phase of the second end by the second amount.

39. The device of claim 36, wherein the processing circuit further comprising a gain stage coupled to the phase shifter and configured to modify an amplitude of at least one of the first end and second end.

40. The device of claim 39, wherein the processing circuit further comprises a limiter stage coupled to the phase shifter and gain stage and configured to limit an amplitude of at least one of the first end and the second end.

41. A phase shifter, comprising:

a first input port;

a second input port, wherein the first and second input ports are configured to receive a differential input signal; and

three output ports configured to provide three respective output signals of substantially equal amplitude and different phase.

42. The phase shifter of claim 41, comprising an RC network including a fixed value resistor and a fixed value capacitor.

43. The phase shifter of claim 42, wherein a first terminal of the resistor is connected to a first terminal of the capacitor and to a first of the three output ports.

44. The phase shifter of claim 43, wherein a second terminal of the resistor is coupled to the first input port and a second of the three output ports.

45. The phase shifter of claim 44, wherein a second terminal of the capacitor is coupled to the second input port and a third of the three output ports.

46. The phase shifter of claim 45, wherein the resistor has a resistance value approximately equal to a negative reactance of the capacitor.

47. The phase shifter of claim 41, wherein the phase shifter does not include a variable capacitor.