SINGLE-RESONATOR DUAL-FREQUENCY LATERAL-EXTENSION MODE PIEZOELECTRIC OSCILLATORS, AND OPERATING METHODS THEREOF

• US 20090072663A1
• Filed: 09/18/2008
• Published: 03/19/2009
• Est. Priority Date: 09/19/2007
• Status: Active Grant

• Current Assignee: Georgia Tech Research Corporation (University System of Georgia)
• Original Assignee: Georgia Tech Research Corporation (University System of Georgia)
• Inventors: Abdolvand, Reza, Ayazi, Farrokh, Lavasani, Seyed Hossein Miri
• Granted Patent: US 7,800,282 B2
• Time in Patent Office: Days
• US Class Current: 310/320
• CPC Class Codes: H03B 2200/0046 including measures to switch the gain of an amplifier
• CPC Class Codes: H03B 2200/0048 including measures to switch the frequency band, e.g. by harmonic selection
• CPC Class Codes: H03B 5/326 the resonator being an acoustic wave device, e.g. SAW or BAW device
• CPC Class Codes: H03B 5/366 and comprising means for varying the frequency by a variable voltage or current
• CPC Class Codes: H03H 2009/02173 of film bulk acoustic resonators [FBAR]
• CPC Class Codes: H03H 2009/02496 Horizontal, i.e. parallel to the substrate plane
• CPC Class Codes: H03H 2009/241 Bulk-mode MEMS resonators
• CPC Class Codes: H03H 9/02228 Guided bulk acoustic wave devices or Lamb wave devices having interdigital transducers situated in parallel planes on either side of a piezoelectric layer
• CPC Class Codes: H03H 9/02259 Driving or detection means
• CPC Class Codes: H03H 9/172 Means for mounting on a substrate, i.e. means constituting the material interface confining the waves to a volume
• CPC Class Codes: H03H 9/2463 Clamped-clamped beam resonators

Abstract

Oscillators include a resonator having first and second electrodes and configured to resonate at a first frequency at which the first and second electrodes carry in-phase signals and at a second frequency at which the first and second electrodes carry out-of-phase signals. A driver circuit is configured to selectively sustain either the in-phase signals on the first and second electrodes or the out-of-phase signals on the first and second electrodes so that the resonator selectively resonates at either the first frequency or the second frequency, respectively. Related oscillator operating methods are also disclosed.

Claims

1. An oscillator comprising:

a resonator that includes first and second electrodes and is configured to resonate at a first frequency at which the first and second electrodes carry in-phase signals and at a second frequency at which the first and second electrodes carry out-of-phase signals; and

a driver circuit that is configured to selectively sustain either the in-phase signals on the first and second electrodes or the out-of-phase signals on the first and second electrodes so that the resonator selectively resonates at either the first frequency or the second frequency, respectively.

2. An oscillator according to claim 1 wherein the resonator comprises a thin-film material that supports a first-order width-extensional resonance mode and a higher-order width-extensional resonance mode.

3. An oscillator according to claim 2 wherein the first and second electrodes are patterned to cause the thin-film material to resonate in either the first-order width-extensional resonance mode or the higher-order width-extensional resonance mode, depending on whether the driver circuit sustains the in-phase signals or the out-of-phase signals, respectively.

4. An oscillator according to claim 3 wherein the first and second electrodes comprise a predetermined number of interdigitated fingers, wherein the predetermined number corresponds to the higher-order resonance mode.

5. An oscillator according to claim 1 wherein the resonator comprises a Thin-film Piezoelectric-on-Substrate (TPoS) resonator.

6. An oscillator according to claim 5 wherein the TPoS resonator comprises:

a substrate;

a single crystal silicon plate that is suspended from the substrate; and

a thin-film piezoelectric layer on the single crystal silicon plate;

wherein the first and second electrodes are on the thin-film piezoelectric layer.

7. An oscillator according to claim 6 wherein the first and second electrodes are patterned to cause the thin-film piezoelectric layer to excite either a first-order width-extensional resonance mode or a higher-order width-extensional resonance mode in the single crystal silicon plate, depending on whether the driver circuit sustains the in-phase signals or the out-of-phase signals, respectively.

8. An oscillator according to claim 7 wherein the first and second electrodes comprise a predetermined number of interdigitated fingers, wherein the predetermined number corresponds to the higher-order resonance mode.

9. An oscillator according to claim 1 wherein the resonator comprises a microelectromechanical system (MEMS) resonator.

10. An oscillator according to claim 1 wherein the driver circuit comprises first and second inverting amplifiers that are serially connected between the first and second electrodes to sustain the in-phase signals, and a switch that is configured to bypass one of the first or second inverting amplifiers to sustain the out-of-phase signals.

11. An oscillator according to claim 10 wherein each of the first and second inverting amplifiers comprises a single active semiconductor device.

12. An oscillator according to claim 1 wherein the out-of-phase signals are 180°

out of phase.

13. An oscillator comprising:

a microelectronic substrate; and

a microelectromechanical system (MEMS) resonator that is suspended from the microelectronic substrate and that is configured to resonate at two different frequencies.

14. An oscillator according to claim 13 wherein the MEMS resonator comprises a plate suspended from the microelectronic substrate and that resonates in a first-order width-extensional resonance mode and a higher-order width-extensional resonance mode.

15. An oscillator according to claim 14 further comprising first and second electrodes on the plate that are patterned to cause the plate to resonate in either the first-order width-extensional resonance mode or the higher-order width-extensional resonance mode, when the electrodes are driven.

16. An oscillator according to claim 15 wherein the first and second electrodes comprise a predetermined number of interdigitated fingers, wherein the predetermined number corresponds to the higher-order resonance mode.

17. An oscillator according to claim 13 wherein the MEMS resonator comprises a Thin-film Piezoelectric-on-Substrate (TPoS) resonator.

18. An oscillator according to claim 17 wherein the TPoS resonator comprises:

a single crystal silicon plate that is suspended from the microelectronic substrate;

a thin-film piezoelectric layer on the single crystal silicon plate; and

first and second electrodes on the thin-film piezoelectric layer.

19. An oscillator according to claim 18 wherein the first and second electrodes are patterned to cause the thin-film piezoelectric layer to excite either a first-order width-extensional resonance mode or a higher-order width-extensional resonance mode in the single crystal silicon plate, when the electrodes are driven.

20. An oscillator according to claim 19 wherein the first and second electrodes comprise a predetermined number of interdigitated fingers, wherein the predetermined number corresponds to the higher-order resonance mode.

21. An oscillator comprising:

a microelectronic substrate;

a single crystal silicon plate that is suspended from the microelectronic substrate;

a thin-film piezoelectric layer on the single crystal silicon plate; and

first and second electrodes on the thin-film piezoelectric layer,

wherein the first and second electrodes are configured to cause the thin-film piezoelectric layer to resonate the single crystal silicon plate at either a first frequency or at a second frequency, when the electrodes are driven.

22. An oscillator according to claim 21 wherein the first and second electrodes are configured to cause the thin-film piezoelectric layer to resonate the single crystal silicon plate at a first frequency at which the first and second electrodes carry in-phase signals and at a second frequency at which the first and second electrodes carry out-of-phase signals.

23. An oscillator according to claim 22 further comprising:

a driver circuit that is configured to selectively sustain either the in-phase signals on the first and second electrodes or the out-of-phase signals on the first and second electrodes so that the single crystal silicon plate selectively resonates at either the first frequency or the second frequency, respectively.

24. An oscillator according to claim 21 wherein the first and second electrodes are patterned to cause the thin-film piezoelectric layer to excite either a first-order width-extensional resonance mode or a higher-order width-extensional resonance mode in the single crystal silicon plate, when the electrodes are driven.

25. An oscillator according to claim 24 wherein the first and second electrodes comprise a predetermined number of interdigitated fingers, wherein the predetermined number corresponds to the higher-order resonance mode.

26. An oscillator according to claim 23 wherein the driver circuit comprises first and second inverting amplifiers that are serially connected between the first and second electrodes to sustain the in-phase signals, and a switch that is configured to bypass one of the first or second inverting amplifiers to sustain the out-of-phase signals.

27. An oscillator according to claim 26 wherein each of the first and second inverting amplifiers comprises a single active semiconductor device.

28. An oscillator according to claim 22 wherein the out-of-phase signals are 180°

out of phase.

29. A method of driving a resonator that includes first and second electrodes connected thereto, the method comprising:

selectively sustaining either in-phase signals on the first and second electrodes or out-of-phase signals on the first and second electrodes to cause the resonator to selectively resonate at either a first frequency or at a second frequency, respectively.

30. A method according to claim 29 wherein selectively sustaining comprises selectively sustaining either the in-phase signals on the first and second electrodes or the out-of-phase signals on the first and second electrodes to cause the resonator to selectively resonate at either a first-order width-extensional resonance mode or a higher-order width-extensional resonance mode.