Methods and apparatus for mechanical resonating structures

• US 8,174,170 B1
• Filed: 04/21/2010
• Issued: 05/08/2012
• Est. Priority Date: 05/13/2009
• Status: Active Grant

• Current Assignee: Analog Devices, Inc.
• Original Assignee: Sand 9, Inc. (Analog Devices, Inc.)
• Inventors: Kuypers, Jan H., Chen, David M., Zolfagharkhani, Guiti, Gaidarzhy, Alexei
• Primary Examiner(s): Dougherty, Thomas
• Application Number:
  US12/764,703
• Time in Patent Office: 748 Days
• Field of Search: 310/345, 310/348, 310/368
• US Class Current: 310/368
• CPC Class Codes: H03H 2009/02251 Design
• CPC Class Codes: H03H 2009/241 Bulk-mode MEMS resonators
• CPC Class Codes: H03H 9/02 Details
• CPC Class Codes: H03H 9/02259 Driving or detection means
• CPC Class Codes: H03H 9/2463 Clamped-clamped beam resonators

Abstract

Mechanical resonating structures and related methods are described. The mechanical resonating structures may provide improved efficiency over conventional resonating structures. Some of the structures have lengths and widths and are designed to vibrate in a direction approximately parallel to either the length or width. They may have boundaries bounding the length and width dimensions, which may substantially align with nodes or anti-nodes of vibration.

Claims

1. A device comprising:

a substantially planar mechanical resonating structure having a length and a width, the mechanical resonating structure operable to exhibit primary vibration having a direction approximately parallel to the length of the mechanical resonating structure and secondary vibration having a direction approximately parallel to the width of the mechanical resonating structure,

wherein sides of the mechanical resonating structure substantially align with nodes of the secondary vibration for a resonance frequency of the mechanical resonating structure.

2. The device of claim 1, wherein ends of the mechanical resonating structure substantially align with anti-nodes of the primary vibration for the resonance frequency.

3. The device of claim 1, wherein the mechanical resonating structure has a substantially rectangular shape.

4. The device of claim 3, wherein the mechanical resonating structure has one or more beveled edges.

5. The device of claim 1, wherein a ratio of the width to a resonant wavelength of the mechanical resonating structure is between approximately 0.6-0.9.

6. The device of claim 1, wherein a ratio of the width to a resonant wavelength of the mechanical resonating structure is between approximately 1.2-1.8.

7. The device of claim 1, wherein the mechanical resonating structure has an operating frequency ranging from 30 to 35 kHz.

8. The device of claim 1, wherein the mechanical resonating structure has an operating frequency ranging from 60 to 70 kHz.

9. The device of claim 1, wherein the mechanical resonating structure has an operating frequency ranging from 100 MHz to 150 MHz.

10. The device of claim 1, wherein the mechanical resonating structure has an operating frequency ranging from 100 MHz to 3 GHz.

11. The device of claim 1, wherein the mechanical resonating structure has an operating frequency ranging from 3 GHz to 10 GHz.

12. The device of claim 1, wherein the mechanical resonating structure comprises a piezoelectric material.

13. The device of claim 12, wherein the piezoelectric material is chosen from the group consisting of:

aluminum nitride (AlN), zinc oxide (ZnO), cadmium sulfide (CdS), lead titanate (PbTiO₃), lead zirconate titanate (PZT), lithium niobate (LiNbO₃), lithium tantalate (LiTaO₃), potassium niobate (KNbO₃), Li₂B₄O₇, langasite (La₃Ga₅SiO₁₄), gallium arsenide (GaAs), barium sodium niobate, bismuth germanium oxide, indium arsenide, and indium antimonide.

14. The device of claim 1, wherein the mechanical resonating structure is a suspended mechanical resonating structure, and wherein the mechanical resonating structure is coupled to a body by one or more anchors.

15. The device of claim 14, wherein at least one of the one or more anchors contacts the mechanical resonating structure at a point that lies substantially on a node of the primary vibration.

16. The device of claim 14, wherein at least one of the one or more anchors contacts the mechanical resonating structure at a point that lies substantially on a node of the secondary vibration.

17. The device of claim 16, wherein the at least one of the one or more anchors contacts the mechanical resonating structure at a point that lies substantially on a node of the primary vibration.

18. The device of claim 1, wherein the length is at least one and a half times as large as the width.

19. The device of claim 1, wherein the sides of the mechanical resonating structure include two sides, and wherein the two sides are each positioned within approximately Λ

/5 of a node of the secondary vibration, where Λ

is a length of a period of displacement in the direction of the secondary vibration.

20. The device of claim 19, wherein each of the two sides is positioned within approximately Λ

/8 of a node of the secondary vibration.

21. The device of claim 20, wherein each of the two sides is positioned within approximately Λ

/9 of a node of the secondary vibration.

22. The device of claim 21, wherein each of the two sides is positioned within approximately Λ

/12 of a node of the secondary vibration.

23. The device of claim 1,

wherein the substantially planar mechanical resonating structure is a suspended mechanical resonating structure, comprises a piezoelectric material, and is coupled to a substrate by one or more anchors contacting one or more of the sides of the mechanical resonating structure,

wherein the mechanical resonating structure is configured to support plate acoustic modes of vibration in which the primary vibration has a magnitude at least two times larger than a magnitude of the secondary vibration, and

wherein at least one of the one or more anchors contacts the mechanical resonating structure at a point lying substantially on a node of the primary vibration and a node of the secondary vibration.

24. The device of claim 1, wherein the mechanical resonating structure has a periphery lying substantially within a first plane, the periphery formed of one or more segments comprising the sides, wherein each of the one or more segments substantially aligns with either a node or anti-node of vibration of a resonance mode of the mechanical resonating structure.

25. The device of claim 24, wherein the mechanical resonating structure comprises a piezoelectric material.

26. The device of claim 24, wherein the mechanical resonating structure is configured to support plate acoustic modes of vibration.

27. The device of claim 24, wherein the mechanical resonating structure has a resonance frequency between approximately 100 MHz and 150 MHz.

28. The device of claim 1, further comprising

an anchor interconnecting the mechanical resonating structure to a body, the anchor positioned to contact a periphery of the mechanical resonating structure at a point positioned approximately on a node of the secondary vibration.

29. The device of claim 28, wherein the anchor interconnecting the mechanical resonating structure to the body is positioned to contact the mechanical resonating structure at a point positioned approximately on a node of the primary vibration.

30. The device of claim 28, wherein a largest dimension of the mechanical resonating structure is less than approximately 1000 microns.

31. The device of claim 30, wherein the mechanical resonating structure is substantially rectangular.

32. The device of claim 30, wherein the body is a substrate.

33. The device of claim 32, wherein the substrate has a cavity formed therein, and wherein the mechanical resonating structure is suspended above the cavity.

34. The device of claim 28, wherein the device comprises a plurality of anchors comprising the anchor, and wherein each of the plurality of anchors contacts the mechanical resonating structure at a respective contact point positioned approximately on a node of vibration of the mechanical resonating structure in the primary direction and on a node of vibration of the mechanical resonating structure in the secondary direction.