METHODS AND APPARATUS FOR TUNING DEVICES HAVING MECHANICAL RESONATORS

• US 20100308931A1
• 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 8,446,227 B2
• Time in Patent Office: Days
• US Class Current: 331/154
• 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 a drive signal using a drive circuit for driving the mechanical resonator;

providing the drive signal to an LC tuning subcircuit having an input coupled to the drive circuit and an output coupled to the mechanical resonator; and

varying a capacitance value of the LC tuning subcircuit.

2. An electromechanical device, comprising:

a mechanical resonator having a parasitic inductance and a parasitic capacitance;

an electrical drive circuit configured to drive the mechanical resonator; and

an LC tuning subcircuit comprising an inductor and a capacitor, the LC tuning subcircuit coupled to the mechanical resonator and configured to adjust a resonance frequency of the electromechanical device.

3. The electromechanical device of claim 2, wherein at least one of the inductor and the capacitor of the LC tuning subcircuit is variable.

4. The electromechanical device of claim 3, wherein the capacitor of the LC tuning subcircuit is a variable capacitor and the inductor of the LC tuning subcircuit has a fixed value.

5. The electromechanical device of claim 4, wherein a reactance of the variable capacitor at a first frequency is variable between a lower reactance value and an upper reactance value, and wherein the inductor has an inductance value such that a reactance of the inductor at the first frequency is equal to a midpoint between the lower reactance value and the upper reactance value.

6. A device, comprising:

a mechanical resonator having a series resonance frequency; and

a tuner coupled to the mechanical resonator and configured to adjust an operating frequency of the device to a frequency less than or greater than the series resonance frequency.

7. The device of claim 6, wherein the device forms at least part of a microelectromechanical system (MEMS).

8. The device of claim 7, wherein the mechanical resonator is actuated at least partially by one of piezoelectric actuation, electrostatic actuation, magnetic actuation, thermal actuation, and piezoresistive actuation.

9. The device of claim 7, wherein oscillation of the mechanical resonator is detected at least partially by one of piezoelectric, electrostatic, magnetic, thermal, and piezoresistive techniques.

10. The device of claim 6, wherein the tuner is configured to adjust the operating frequency of the device over a range of at least 400 parts per million of the series resonance frequency.

11. The device of claim 10, wherein the tuner is configured to adjust the operating frequency of the device over a range of at least 500 parts per million of the series resonance frequency.

12. The device of claim 11, wherein the tuner is configured to adjust the operating frequency of the device over a range of between approximately 500 parts per million and 700 parts per million of the series resonance frequency.

13. The device of claim 12, wherein the tuner is configured to adjust the operating frequency of the device over a range of between approximately 600 parts per million and 800 parts per million of the series resonance frequency.