Cross-quad and vertically coupled inertial sensors

• US 7,421,897 B2
• Filed: 04/14/2005
• Issued: 09/09/2008
• Est. Priority Date: 04/14/2005
• Status: Active Grant

• Current Assignee: Analog Devices, Inc.
• Original Assignee: Analog Devices, Inc.
• Inventors: Kuang, Jinbo, Geen, John A.
• Primary Examiner(s): Kwok; Helen C.
• Application Number:
  US11/106,053
• Publication Number:
  US 20060230830A1
• Time in Patent Office: 1,244 Days
• Field of Search: 735/040.2, 735/040.4, 735/041.2, 735/041.4, 735/041.6, 735/143.2, 735/143.8, 735/143.6, 735/141.6, 735/142.9
• US Class Current: 73/504.12
• CPC Class Codes: G01C 19/574 the devices having two sensing masses in anti-phase motion

Abstract

An inertial sensor includes a cross-quad configuration of four interconnected sensor elements. Each sensor element has a frame and a resonator suspended within the frame. The sensor elements are arranged so that the frames of adjacent sensor elements are allowed to move in anti-phase to one another but are substantially prevented from moving in phase with one another. The sensor elements may be configured in a horizontally coupled arrangement, a vertically coupled arrangement, or a fully coupled arrangement. A pair of sensor elements may be vertically coupled.

Claims

1. An inertial sensor comprising:

at least one substrate; and

four sensor elements arranged in a cross-quad configuration substantially in a plane above the at least one substrate, the four sensor elements including;

a first sensor element having a first resonator suspended within a first frame;

a second sensor element having a second resonator suspended within a second frame;

a third sensor element having a third resonator suspended within a third frame; and

a fourth sensor element having a fourth resonator suspended within a fourth frame, wherein the first and third frames are configured to move co-linearly along a first axis in the plane, the second and fourth frames are configured to move co-linearly along a second axis in the plane parallel to the first axis, and the frames of at least two pairs of adjacent sensor elements are interconnected by couplings that enable anti-phase movements of the frames but substantially prevent in-phase movements of the frames.

2. An inertial sensor according to claim 1, wherein:

the first and second resonators are caused to move co-linearly and in anti-phase to one another along a third axis normal to the first and second axes in the plane;

the third and fourth resonators are caused to move co-linearly and in anti-phase to one another along a fourth axis parallel to the third axis in the plane;

the first and third resonators are caused to move in anti-phase to one another; and

the second and fourth resonators are caused to move in anti-phase to one another.

3. An inertial sensor according to claim 1, wherein rotation of the at least one substrate about an axis normal to the plane causes the movements of the frames.

4. An inertial sensor according to claim 3, wherein:

rotation of the substrate in a first direction causes the first and third frames to move toward one another and the second and fourth frames to move away from one another while the first and second resonators move toward each other; and

rotation of the substrate in a second direction causes the first and third frames to move away from one anther and the second and fourth frames to move toward one another while the first and second resonators move toward each other.

5. An inertial sensor according to claim 1, wherein:

the first and second frames are interconnected by a first horizontal coupling that enables anti-phase movements of the frames along the frame'"'"'s respective axes but substantially prevents in-phase movements of the frames; and

the third and fourth frames are interconnected by a second horizontal coupling that enables anti-phase movements of the frames along the frame'"'"'s respective axes but substantially prevents in-phase movements of the frames.

6. An inertial sensor according to claim 5, wherein each of the first and second horizontal couplings comprises:

at least one bar coupled between the first and second frames, the at least one bar supported by structures anchored to the at least one substrate, the structures allowing the at least one bar to rotate at a pivot point when the frames move in anti-phase to one another but substantially preventing in-phase movements of the frames.

7. An inertial sensor according to claim 6, wherein each of the first and second horizontal couplings includes:

a first pair of short flexures extending from one of the frames and interconnected by a first long flexure;

a second pair of short flexures extending from the other of the frames and interconnected by a second long flexure;

a bar coupling the first long flexure to the second long flexure substantially at the midpoints of the first and second long flexures; and

an anchor flexure supporting the bar, the anchor flexure intersecting with the bar substantially at the midpoints of the bar and the anchor flexure, each end of the anchor flexure anchored to the substrate.

8. An inertial sensor according to claim 6, wherein each of the first and second horizontal couplings includes:

a first flexure extending from one of the frames;

a second flexure extending from the other of the frames;

a bar coupled between the first and second flexures; and

at least one anchor flexure supporting the bar, each of the at least one anchor flexure including a structure anchored at one end to the at least one substrate and folded back 180 degrees to meet with the bar.

9. An inertial sensor according to claim 1, wherein:

the first and third frames are interconnected by a first vertical coupling that enables anti-phase movements of the frames along the frame'"'"'s co-linear axis but substantially prevents in-phase movements of the frames; and

the second and fourth frames are interconnected by a second vertical coupling that enables anti-phase movements of the frames along the frame'"'"'s co-linear axis but substantially prevents in-phase movements of the frames.

10. An inertial sensor according to claim 9, wherein each of the first and second vertical couplings includes:

a first pair of interconnected levers coupled to one of the frames, the first pair of levers including a first lever and a second lever;

a second pair of interconnected levers coupled to the other of the frames, the second pair of levers including a third lever and a fourth lever;

a plurality of lever support structures allowing the levers to pivot as the frames move in anti-phase to one another;

a first coupling flexure interconnecting the first lever and the third lever substantially between the lever'"'"'s respective pivot points; and

a second coupling flexure interconnecting the second lever and the fourth lever substantially between the lever'"'"'s respective pivot points, wherein the coupling flexures substantially prevent in-phase movements of the frames.

11. An inertial sensor according to claim 10, wherein both ends of each coupling flexure move transversely to the movements of the frames in the same direction by substantially the same amount during anti-phase movements of the frames but are urged to move in opposite directions during in-phase movements of the frames.

12. An inertial sensor according to claim 10, wherein the plurality of lever support structures include:

at least one pivot flexure coupled at one end to a lever and at another end to a structure anchored to the substrate.

13. An inertial sensor according to claim 12, wherein the at least one pivot flexure includes a first pivot flexure and a second pivot flexure interconnected at a point.

14. An inertial sensor according to claim 13, wherein the interconnection point is toward a middle of the lever.

15. An inertial sensor according to claim 13, wherein the interconnection point is toward an edge of the lever nearest the frame.

16. An inertial sensor according to claim 13, wherein:

the first coupling flexure is substantially in line with the interconnection points of the first and third levers; and

the second coupling flexure is substantially in line with the interconnection points of the second and fourth levers.

17. An inertial sensor according to claim 12, wherein the structure anchored to the substrate is a bar anchored to the substrate.

18. An inertial sensor according to claim 10, wherein each pair of levers is interconnected by a lever flexure.

19. An inertial sensor according to claim 10, wherein each lever is connected to the lever'"'"'s respective frame by a suspension flexure.

20. An inertial sensor according to claim 1, wherein each frame includes finger structures that interdigitate with fixed sensing fingers anchored to the at least one substrate for electrostatically sensing the movements of the frames.

21. An inertial sensor according to claim 1, wherein each resonator includes finger structures that interdigitate with fixed drive fingers anchored to the at least one substrate for electrostatically moving the resonator.

22. An inertial sensor according to claim 1, wherein:

the first and second frames are interconnected by a first horizontal coupling that enables anti-phase movements of the frames along the frame'"'"'s respective axes but substantially prevents in-phase movements of the frames;

the third and fourth frames are interconnected by a second horizontal coupling that enables anti-phase movements of the frames along the frame'"'"'s respective axes but substantially prevents in-phase movements of the frames;

the first and third frames are interconnected by a first vertical coupling that enables anti-phase movements of the frames along the frame'"'"'s co-linear axis but substantially prevents in-phase movements of the frames; and

the second and fourth frames are interconnected by a second vertical coupling that enables anti-phase movements of the frames along the frame'"'"'s co-linear axis but substantially prevents in-phase movements of the frames.

23. An inertial sensor comprising:

at least one substrate; and

four sensor elements arranged in a cross-quad configuration substantially in a plane above the at least one substrate, the four sensor elements including;

a first sensor element having a first resonator suspended within a first frame;

a second sensor element having a second resonator suspended within a second frame;

a third sensor element having a third resonator suspended within a third frame; and

a fourth sensor element having a fourth resonator suspended within a fourth frame, wherein the first and third frames are configured to move co-linearly along a first axis in the plane and the second and fourth frames are configured to move co-linearly along a second axis in the plane parallel to the first axis;

first means for interconnecting the frames of a first pair of adjacent sensor elements to enable anti-phase movements of the frames but substantially prevent in-phase movements of the frames; and

second means for interconnecting the frames of a second pair of adjacent sensor elements to enable anti-phase movements of the frames but substantially prevent in-phase movements of the frames.

24. An inertial sensor according to claim 23, further comprising:

third means for interconnecting the frames of a third pair of adjacent sensor elements to enable anti-phase movements of the frames but substantially prevent in-phase movements of the frames; and

fourth means for interconnecting the frames of a fourth pair of adjacent sensor elements to enable anti-phase movements of the frames but substantially prevent in-phase movements of the frames.

25. An inertial sensor comprising:

at least one substrate;

a pair of sensor elements substantially in a plane above the at least one substrate, each sensor element having a resonator suspended within a frame, the frames configured to move co-linearly along an axis in the plane; and

a vertical coupling, interconnecting the frames, that enables anti-phase movements of the frames along the frame'"'"'s co-linear axis but substantially prevents in-phase movements of the frames.

26. An inertial sensor according to claim 25, wherein the vertical coupling includes:

a first pair of interconnected levers coupled to one of the frames, the first pair of levers including a first lever and a second lever;

a second pair of interconnected levers coupled to the other of the frames, the second pair of levers including a third lever and a fourth lever;

a plurality of lever support structures allowing the levers to pivot as the frames move in anti-phase to one another;

a first coupling flexure interconnecting the first lever and the third lever substantially at the lever'"'"'s respective pivot points; and

a second coupling flexure interconnecting the second lever and the fourth lever substantially at the lever'"'"'s respective pivot points, wherein the coupling flexures substantially prevent in-phase movements of the frames.