A. Technical Field
The present invention relates to high-Q Micro Electro Mechanical System (MEMS) sensors and, more particularly, to systems, devices, and methods of reducing resonance effects in high-Q MEMS sensors operating in spot mode.
B. Background of the Invention
A new generation of high performance, low power MEMS sensors is playing an increasingly important role in the consumer electronics market. Miniaturization efforts drive the integration of multiple navigational sensors, such as accelerometers, magnetometers, and gyroscopes, into a single package. Some inertial sensor applications that use stand-alone accelerometers in inclinometers, fall detection sensors, etc., employ spot mode operation techniques in order to reduce power consumption. Transitions between ON and OFF states within spot mode operation involve relatively rapid changes in sensor bias conditions that give rise to perturbations, which may cause unwanted oscillations that negatively impact settling times. In accelerometers sensor with movable proof-mass perturbations are greatly amplified when excitation frequencies coincide with resonance frequencies of high-Q mechanical resonator systems that comprise a proof-mass.
For these stand-alone accelerometers, existing solutions include utilizing atmospheric pressure inside the sensor cavity, which increases friction and lowers the quality factor of the mechanical resonator system so as to avoid oscillations or, at least, sufficiently reduce unwanted oscillations in order to achieve faster setting times.
Unfortunately, for MEMS gyroscope sensors, high Q is a crucial and wanted design parameter. In fact, these sensors are generally assembled and operated under vacuum conditions. Therefore, in an integrated accelerometer-gyroscope sensor system, as a tradeoff, the quality factor of a MEMS accelerometer sensor typically gives way to the requirements of the gyroscope since the quality factor of the MEMS accelerometer cannot be made sufficiently low so as to avoid unwanted high-Q oscillations during accelerometer spot mode operation.
What is needed are tools for system designers to overcome the above-described limitations.