OFFSET REJECTION ELECTRODES

• US 20160334438A1
• Filed: 05/15/2015
• Published: 11/17/2016
• Est. Priority Date: 05/15/2015
• Status: Active Grant

• Current Assignee: Invensense Incorporated (TDK Corporation)
• Original Assignee: Invensense Incorporated (TDK Corporation)
• Inventors: THOMPSON, Matthew Julian, WILLIAMS, Kirt Reed
• Granted Patent: US 9,952,252 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: B81B 2201/025 Inertial sensors not provided for in B81B2201/0235 - B81B2201/0242
• CPC Class Codes: B81B 2203/0307 Anchors
• CPC Class Codes: B81B 2203/04 Electrodes
• CPC Class Codes: B81B 3/0086 Electrical characteristics, e.g. reducing driving voltage, improving resistance to peak voltage
• CPC Class Codes: B81B 7/0016 Protection against shocks or vibrations, e.g. vibration damping
• CPC Class Codes: G01P 15/125 by capacitive pick-up
• CPC Class Codes: G01P 2015/0831 the mass being of the paddle type having the pivot axis between the longitudinal ends of the mass, e.g. see-saw configuration

Abstract

A system and method for reducing offset in a MEMS sensor are disclosed. In a first aspect, the system is a MEMS sensor that comprises a sensing reference plane, at least one anchor coupled to the sensing reference plane, at least one proof mass coupled to the at least one anchor, wherein one of the at least one proof mass moves under an external excitation, a pattern of sensing elements coupled between the sensing reference plane and the at least one proof mass to detect motion normal to the sensing reference plane, wherein the pattern of sensing elements shares at least three axes of polarity anti-symmetry, and a signal processing circuit to combine the pattern of sensing elements thereby providing an output proportional to the external excitation. In a second aspect, the sensing reference plane is divided by two axes forming four quadrants on the sensing reference plane.

Claims

1. A MEMS sensor, comprising:

a sensing reference plane;

at least one anchor coupled to the sensing reference plane;

at least one proof mass coupled to the at least one anchor, wherein one of the at least one proof mass moves under an external excitation;

a pattern of sensing elements coupled between the sensing reference plane and the at least one proof mass to detect motion normal to the sensing reference plane, wherein the pattern of sensing elements shares at least three axes of polarity anti-symmetry; and

a signal processing circuit to combine the pattern of sensing elements thereby providing an output proportional to the external excitation.

2. The MEMS sensor of claim 1, wherein the centroid of each sensing element shares a common distance to a center of the at least one anchor.

3. The MEMS sensor of claim 1, wherein the pattern of sensing elements comprises sensing electrodes forming a variable capacitor between each electrode and the at least one proof mass.

4. The MEMS sensor of claim 1, wherein the pattern of sensing elements comprises at least three positive sensing elements and at least three negative sensing elements that are alternating.

5. The MEMS sensor of claim 1, wherein each sensing element is a magnetic sensing element.

6. The MEMS sensor of claim 1, wherein the center of each sensing element is on a perimeter of any of a circle, rectangle, square, hexagon, octagon, and other polygon.

7. The MEMS sensor of claim 1, wherein each sensing element is any of circular, rectangular, square, hexagonal, octagonal, annular sector, and polygonal in shape.

8. The MEMS sensor of claim 4, wherein each negative sensing element has the same area as each positive sensing element.

9. The MEMS sensor of claim 2, further comprising:

a second pattern of sensing elements on the sensing reference plane to detect the motion of the at least one proof mass relative to the sensing reference plane, wherein the second pattern of sensing elements shares at least three axes of polarity anti-symmetry.

10. The MEMS sensor of claim 9, wherein the centroid of each sensing element of the second pattern of sensing elements shares a second common distance to the center of the at least one anchor.

11. A MEMS sensor, comprising:

a sensing reference plane, wherein the sensing reference plane is divided by a first and a second axis forming four quadrants on the sensing reference plane;

at least one anchor coupled to the sensing reference plane;

at least one proof mass coupled to the at least one anchor, wherein one of the at least one proof mass moves under an external excitation; and

a pattern of sensing elements on the sensing reference plane to detect motion of the at least one proof mass relative to the sensing reference plane, wherein the pattern of sensing elements comprises at least three sensing elements in each of the four quadrants.

12. The MEMS sensor of claim 11, wherein in each of the four quadrants the closest sensing element and the furthest sensing element, relative to one of the first or second axes, is of a first polarity and in between the first polarity there is at least one sensing element of a second polarity.

13. The MEMS sensor of claim 12, wherein the first polarity is opposite of the second polarity.

14. The MEMS sensor of claim 11, wherein there is polarity anti-symmetry of the four quadrants about at least one of the first or the second axis.

15. The MEMS sensor of claim 11, wherein a center of the at least one anchor coincides with an intersection of the first and the second axis.

16. The MEMS sensor of claim 11, wherein a centroid of the at least three sensing elements in each of the four quadrants shares a common distance from at least one of the first or the second axis.

17. The MEMS sensor of claim 11, wherein each of the at least three sensing elements are any of circular, rectangular, square, hexagonal, octagonal, annular sectors, and polygonal in shape.

18. The MEMS sensor of claim 13, wherein a sensing element area is substantially the same between the first and the second polarity.

19. The MEMS sensor of claim 12, wherein the pattern of sensing elements comprises sensing electrodes forming a variable capacitor between each electrode and the at least one proof mass.