Differential z-axis resonant accelerometry
AssigneeAnalog Devices, Inc.
InventorMehrnaz Motiee
Life of this patent
Estimating the term…
Abstract
A MEMS resonant accelerometer includes two proof masses configured to resonate when driven with periodic signals. Each proof mass includes a resonator structure that vibrates relative to the proof mass and a dummy structure that does not resonate. When driven by a periodic drive signal, the resonator structures of the two proof masses may be used to determine the magnitude of acceleration in the direction perpendicular to the planes of the proof masses by sensing the frequency at which the resonators vibrate. For example, a differential oscillation frequency may be computed from the two sensed frequencies. The dummy structures are used to make the mass distribution of the two proof masses similar.
Claims20
A microelectromechanical system (MEMS) accelerometer comprising:
- a first teeter-totter structure, comprising:
- a first proof mass coupled to a substrate through a first anchor, the first proof mass having first and second mass portions having different masses and disposed at opposite sides of the first proof mass with respect to the first anchor;
- a first resonator structure pivotally attached to the first proof mass and configured to vibrate relative to the first proof mass;
- and
- a first dummy structure fixedly attached to the first proof mass;
- and
- a second teeter-totter structure, comprising:
- a second proof mass coupled to the substrate through a second anchor, the second proof mass having third and fourth mass portions having different masses and disposed at opposite sides of the second proof mass with respect to the second anchor;
- a second resonator structure pivotally attached to the second proof mass and configured to vibrate relative to the second proof mass;
- and
- a second dummy structure fixedly attached to the second proof mass.
A microelectromechanical system (MEMS) device comprising:
- an accelerometer comprising:
- a first teeter-totter structure, comprising:
- a first proof mass coupled to a substrate through a first anchor, the first proof mass having first and second mass portions having different masses and disposed at opposite sides of the first proof mass with respect to the first anchor;
- a first resonator structure pivotally attached to the first proof mass and configured to resonate relative to the first proof mass;
- and
- a first dummy structure fixedly attached to the first proof mass;
- and
- a second teeter-totter structure, comprising:
- a second proof mass coupled to the substrate through a second anchor, the second proof mass having third and fourth mass portions having different masses and disposed at opposite sides of the second proof mass with respect to the second anchor;
- a second resonator structure pivotally attached to the second proof mass and configured to vibrate relative to the second proof mass;
- and
- a second dummy structure fixedly attached to the second proof mass.
A method for sensing accelerations using a microelectromechanical system (MEMS) accelerometer, the method comprising:
- causing a first resonator structure to vibrate out-of-plane by vibrating about a first axis, wherein the first resonator structure is coupled to a first proof mass that includes a first dummy structure that is the same mass as the first resonator structure;
- causing a second resonator structure to vibrate out-of-plane by vibrating about a second axis, wherein the second resonator structure is coupled to a second proof mass that includes a second dummy structure that is the same mass as the second resonator structure;
- sensing a first oscillation frequency of the first resonator structure and a second oscillation frequency of the second resonator structure;
- and
- computing a differential oscillation frequency from the first and second oscillation frequencies.
Dependencies are inferred from the claim text.