Micromachined apparatus with co-linear drive arrays

• US 7,357,025 B2
• Filed: 02/23/2006
• Issued: 04/15/2008
• Est. Priority Date: 02/06/2002
• Status: Expired due to Term

• Current Assignee: Analog Devices, Inc.
• Original Assignee: Analog Devices, Inc.
• Inventors: Geen, John A.
• Primary Examiner(s): KWOK, HELEN C
• Application Number:
  US11/360,847
• Publication Number:
  US 20060179945A1
• Time in Patent Office: 782 Days
• Field of Search: 735/040.4, 735/041.2, 735/041.4, 735/041.5, 735/041.6, 735/143.2, 735/143.6, 735/143.8
• US Class Current: 73/504.12
• CPC Class Codes: G01C 19/5719 using planar vibrating masses driven in a translation vibration along an axis
• CPC Class Codes: Y10T 74/12 Gyroscopes

Abstract

A mass includes a first set of drive fingers interdigitated with a first array of fixed drive fingers and a second set of drive fingers interdigitated with a second array of fixed drive fingers. Each array of fixed drive fingers is affixed to a substrate using a plurality of anchors. The anchors for the first and second arrays of fixed drive fingers are arranged to be co-linear in a lateral direction relative to the motion of the mass.

Claims

1. Apparatus comprising:

a substrate; and

a plurality of resonator structures, the resonator structures including at least one mass movable relative to the substrate, the resonator structures further including a drive arrangement for each mass, the drive arrangement including a first electrode oriented in a first direction and a second electrode oriented in a second direction opposite the first direction, wherein each of the first and second electrodes is affixed to the substrate using a plurality of anchors, and wherein the anchors for the first and second electrodes are arranged to be co-linear in a lateral direction relative to the motion of the mass.

2. Apparatus according to claim 1, wherein each anchor has a top end substantially in the plane of motion of at least one mass and a substrate end mechanically joined to the substrate, and wherein the anchors are laid down in pairs joined to each other at the top ends remote from the substrate so that the top end of each anchor resists twisting at the substrate end.

3. Apparatus according to claim 2, wherein each electrode includes a busbar, and wherein the busbars are attached to the top ends of the anchors by flexible, folded fingers.

4. Apparatus according to claim 1, wherein the drive arrangement further includes a third electrode oriented in the first direction and a fourth electrode oriented in the second direction, wherein each of the third and fourth electrodes is affixed to the substrate using a plurality of anchors, and wherein the anchors for the third and fourth electrodes are arranged to be co-linear in a lateral direction relative to the motion of the mass.

5. Apparatus according to claim 4, wherein the anchors for the third and fourth electrodes are arranged to be co-linear with the anchors for the first and second electrodes.

6. Apparatus according to claim 1, wherein the resonator structures include a pair of masses that resonate substantially in phase with one another, and wherein the anchors for the electrodes for the pair of masses are arranged to be co-linear in a lateral direction relative to the motions of the masses.

7. Apparatus according to claim 1, wherein the resonator structures include a first pair of masses coupled through a first flexure and a second pair of masses coupled through a second flexure, wherein the first and second pairs of masses are interconnected through a plurality of levers so as to resonate in anti-phase with one another.

8. Apparatus according to claim 7, wherein each mass is coupled to a frame by a suspension flexure, and wherein the first and second flexures allow the masses to rotate slightly as the masses resonate so as to reduce longitudinal stresses in the suspension flexures and levers.

9. Apparatus according to claim 7, wherein the plurality of levers transform the coupled motion of the resonator structures from co-linear motion to parallel motion.

10. Apparatus according to claim 9, wherein each of the plurality of levers is coupled at one end to a frame and at another end to a different one of the masses, and wherein each lever has pivots, defined at the points of attachment to the frame and the mass by the intersection of the axes of at least two orthogonal flexures, to ensure that the attachment point cannot translate with respect to the lever.

11. Apparatus according to claim 9, wherein each of the levers includes a plurality of lever fingers interdigitated with corresponding fingers affixed to an underlying substrate for at least one of driving the lever and sensing position of the lever.

12. Apparatus according to claim 11, wherein each of the levers moves with an arcuate motion, and wherein the lever fingers are disposed at varying angles so as to maintain substantially equal distances from said corresponding affixed fingers during movement of the levers.

13. Apparatus according to claim 7, wherein the masses are electrically coupled through common drive and velocity sensing circuits such as to resonate at substantially a single frequency.

14. Apparatus according to claim 1, wherein each mass comprises at least one notch for electronic quadrature suppression.

15. Apparatus according to claim 14, further comprising:

a plurality of quadrature suppression electrodes, each quadrature suppression electrode positioned adjacent to a respective notch, each quadrature suppression electrode capable of applying a lateral force to the respective notch, the lateral force varying as the mass comprising the respective notch moves relative to the quadrature suppression electrode.

16. Apparatus according to claim 1, further comprising:

a plurality of accelerometer suspension flexures coupled to a frame for suspending the frame from the substrate, the accelerometer suspension flexures designed so as to restrict translational movement of the frame in the plane of the substrate and to allow rotational movement of the frame in the plane of the substrate, wherein rotational movement of the apparatus in the plane of the substrate causes rotation of the frame relative to the substrate in the plane of the substrate.

17. Apparatus according to claim 16, further comprising:

a plurality of frame fingers disposed along an outer perimeter of the frame, the frame fingers interdigitated with corresponding sensing fingers affixed to the substrate for sensing rotational movement of the frame.

18. Apparatus according to claim 17, wherein the outer perimeter of the frame is substantially square and includes a plurality of frame fingers disposed along each side of the frame.

19. Apparatus according to claim 18, wherein the frame fingers are disposed at varying angles so as to maintain substantially equal distances from said corresponding sensing fingers during rotational movement of the frame.

20. Apparatus according to claim 17, wherein the accelerometer suspension flexures are arranged at corners of the frame.

21. Apparatus according to claim 1, wherein the plurality of resonator structures are micromachined from a single wafer.