ANGULAR RATE SENSOR WITH QUADRATURE ERROR COMPENSATION

• US 20140374849A1
• Filed: 06/24/2013
• Published: 12/25/2014
• Est. Priority Date: 06/24/2013
• Status: Active Grant

• Current Assignee: NXP USA, Inc. (NXP Semiconductors NV)
• Original Assignee: Freescale Semiconductor, Inc. (NXP Semiconductors NV)
• Inventors: Lin, Yizhen
• Granted Patent: US 9,476,711 B2
• Time in Patent Office: Days
• US Class Current: 257/415
• CPC Class Codes: G01C 19/5712 the devices involving a micromechanical structure
• CPC Class Codes: G01C 19/5726 Signal processing
• CPC Class Codes: G01C 19/574 the devices having two sensing masses in anti-phase motion
• CPC Class Codes: G01C 19/5747 each sensing mass being connected to a driving mass, e.g. driving frames
• CPC Class Codes: G01C 19/5762 the sensing mass being connected to a driving mass, e.g. driving frames

Abstract

An angular rate sensor includes a substrate, a drive mass flexibly coupled to the substrate, and a sense mass suspended above the substrate and flexibly coupled to the drive mass via flexible support elements. An electrode structure is mechanically coupled to, but electrically isolated from, the drive mass and is spaced apart from the substrate so that it is not in contact with the substrate. The electrode structure is configured to produce a signal that indicates movement of the sense mass relative to the electrode when the sensor is subjected to angular velocity. When the angular rate sensor experiences quadrature error, the drive mass, the sense mass, and the electrode structure move together relative to the sense axis. Since the sense mass and the electrode structure move together in response to quadrature error, there is little relative motion between the sense mass and the electrode structure so that quadrature error is largely eliminated.

Claims

1. An angular rate sensor comprising:

a substrate;

a drive mass flexibly coupled to said substrate;

a sense mass suspended above said substrate and flexibly coupled to said drive mass via flexible support elements; and

an electrode structure coupled to said drive mass and spaced apart from said substrate, said electrode structure being configured to produce a sense signal that indicates movement of said sense mass relative to said electrode structure.

2. An angular rate sensor as claimed in claim 1 wherein:

said drive mass and said electrode structure are configured to move together with an oscillatory motion relative to a drive axis;

said flexible support elements enable said sense mass to oscillate relative to a sense axis that is perpendicular to said drive axis in response to an angular velocity about an input axis that is perpendicular to each of said drive and said sense axes, wherein oscillation of said sense mass in response to said angular velocity produces said sense signal between said sense mass and said electrode structure; and

said drive mass, said sense mass, and said electrode structure move together along said sense axis in response to quadrature error to reduce an effect of said quadrature error on said sense signal.

3. An angular rate sensor as claimed in claim 1 wherein said electrode structure is not in contact with said substrate.

4. An angular rate sensor as claimed in claim 1 wherein said electrode structure is electrically isolated from said drive mass.

5. An angular rate sensor as claimed in claim 1 wherein said electrode structure is interposed between said sense mass and a surface of said substrate.

6. An angular rate sensor as claimed in claim 1 wherein said substrate includes a cavity extending inwardly from a surface of said substrate, said drive mass and said sense mass are suspended above said cavity, and said electrode structure is interposed between said cavity and said drive and sense masses.

7. An angular rate sensor as claimed in claim 1 wherein:

said drive mass comprises a frame structure having a central opening;

said sense mass resides in said central opening; and

said electrode structure comprises a sense plate fixedly attached to said drive mass and extending across at least a portion of said central opening proximate said sense mass.

8. An angular rate sensor as claimed in claim 7 wherein:

said sense plate is a first sense plate;

said drive mass includes first and second regions separated by an axis of rotation oriented parallel to a surface of said substrate;

said sense mass includes third and fourth regions separated by said axis of rotation, said first and third regions being disposed on a first side of said axis of rotation, and said second and fourth regions being disposed on a second side of said axis of rotation;

said first sense plate is coupled to said first region of said drive mass and extends across said third region of said sense mass; and

said electrode structure further comprises a second sense plate coupled to said second region of said drive mass, said second sense plate extending across said fourth region of said sense mass.

9. An angular rate sensor as claimed in claim 1 wherein said electrode structure comprises a first finger electrode fixedly attached to a first edge of said drive mass and suspended above a surface of said substrate, said first finger electrode being laterally disposed away from said sense mass.

10. An angular rate sensor as claimed in claim 9 wherein said electrode structure further comprises a second finger electrode fixedly attached to said first edge of said drive mass and suspended above said surface of said substrate, said second finger electrode being laterally disposed away from each of said sense mass and said first finger electrode.

11. An angular rate sensor as claimed in claim 10 wherein said first and second finger electrodes are electrically isolated from one another.

12. An angular rate sensor as claimed in claim 10 wherein said electrode structure further comprises:

a third finger electrode;

a fourth finger electrode, each of said third and fourth finger electrodes being fixedly attached to said first edge of said drive mass, said each of said third and fourth finger electrodes being suspended above said surface of said electrode;

a first interconnect electrically coupling said first finger electrode with said third finger electrode; and

a second interconnect electrically coupling said second finger electrode with said fourth finger electrode, wherein said first and third finger electrodes are electrically isolated from said second and fourth finger electrodes.

13. An angular rate sensor as claimed in claim 12 wherein said first and second interconnects are spaced apart from said surface of said substrate.

14. An angular rate sensor comprising:

a substrate;

a drive mass flexibly coupled to said substrate;

a sense mass suspended above said substrate and flexibly coupled to said drive mass via flexible support elements; and

an electrode structure coupled to said drive mass and spaced apart from said substrate so that said electrode structure is not in contact with said substrate, said electrode structure being electrically isolated from said drive mass, and said electrode structure being configured to produce a sense signal that indicates movement of said sense mass relative to said electrode structure.

15. An angular rate sensor as claimed in claim 14 wherein:

said drive mass comprises a frame structure having a central opening;

said sense mass resides in said central opening; and

said electrode structure comprises a sense plate fixedly attached to said drive mass and extending across at least a portion of said central opening proximate said sense mass.

16. An angular rate sensor as claimed in claim 14 wherein said electrode structure comprises a finger electrode fixedly attached to a first edge of said drive mass and suspended above a surface of said substrate, said finger electrode being laterally disposed away from said sense mass.

17. An angular rate sensor comprising:

a substrate;

a drive mass flexibly coupled to said substrate;

a sense mass suspended above said substrate and flexibly coupled to said drive mass via flexible support elements; and

an electrode structure coupled to said drive mass and spaced apart from said substrate, said electrode structure being electrically isolated from said drive mass, and said electrode structure being configured to produce a sense signal that indicates movement of said sense mass relative to said electrode structure, wherein;

said drive mass and said electrode structure are configured to move together with an oscillatory motion relative to a drive axis;

said flexible support elements enable said sense mass to oscillate relative to a sense axis that is perpendicular to said drive axis in response to an angular velocity about an input axis that is perpendicular to each of said drive and said sense axes, wherein oscillation of said sense mass in response to said angular velocity produces said sense signal between said sense mass and said electrode structure; and

said drive mass, said sense mass, and said electrode structure move together along said sense axis in response to quadrature error to reduce an effect of said quadrature error on said sense signal.

18. An angular rate sensor as claimed in claim 17 wherein.

said drive mass comprises a frame structure having a central opening, said drive mass including first and second regions separated by an axis of rotation oriented parallel to a surface of said substrate;

said sense mass resides in said central opening, said sense mass includes third and fourth regions separated by said axis of rotation, said first and third regions being disposed on a first side of said axis of rotation, and said second and fourth regions being disposed on a second side of said axis of rotation; and

said electrode structure comprises a first sense plate and a second sense plate, said first sense plate being coupled to said first region of said drive mass and extending across said third region of said sense mass, and said second sense plate being coupled to said second region of said drive mass and extending across said fourth region of said sense mass.

19. An angular rate sensor as claimed in claim 17 wherein said electrode structure comprises:

a first finger electrode fixedly attached to a first edge of said drive mass and suspended above a surface of said substrate, said first finger electrode being laterally disposed away from said sense mass; and

a second finger electrode fixedly attached to said first edge of said drive mass and suspended above said surface of said substrate, said second finger electrode being laterally disposed away from each of said sense mass and said first finger electrode.

20. An angular rate sensor as claimed in claim 19 further comprising:

a third finger electrode;

a fourth finger electrode, each of said third and fourth finger electrodes being fixedly attached to said first edge of said drive mass, said each of said third and fourth finger electrodes being suspended above said surface of said substrate;

a first interconnect electrically coupling said first finger electrode with said third finger electrode; and

a second interconnect electrically coupling said second finger electrode with said fourth finger electrode, wherein said first and third finger electrodes are electrically isolated from said second and fourth finger electrodes.