MEMS Gyroscope Gain Circuit for Quality Factor Compensation
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Solution Overview
Problem
Fluctuations in temperature or outgassing/ingassing cause pressure changes in MEMS resonators, leading to changes in the quality factor, which affect the zero-rate offset of MEMS gyroscope, particularly in frequency-mismatched devices, resulting in phase errors.
Innovation Solution
A circuit comprising a microelectromechanical (MEMS) gyroscope and a gain circuit that compensates for changes in the quality factor by determining a percentage change based on a digitized drive signal and a stored trim value, using either drive ratio or drive amplitude to adjust the output signal and phase of the demodulator, thereby correcting for offset and phase errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pressure changes in the MEMS resonator cavity occur due to temperature fluctuations or outgassing/ingassing, then the quality factor of the MEMS resonator changes, but this results in changes to the zero-rate offset and phase errors in frequency-mismatched MEMS gyroscopes
Solution Approach 1:
The patent implements a feedback mechanism where the measured quality factor is used to dynamically adjust the drive amplitude. The system continuously monitors the quality factor through the drive signal and adjusts the drive amplitude accordingly to maintain optimal operation and minimize zero-rate offset errors, creating a closed-loop control system that compensates for environmental variations.
Solution Approach 2:
The patent changes the drive amplitude parameter based on the measured quality factor. By dynamically adjusting the drive amplitude in response to quality factor variations, the system compensates for the effects of pressure changes and temperature fluctuations, maintaining measurement accuracy despite environmental conditions.
2Measurement precision
If the drive amplitude is increased to improve signal strength, then the signal-to-noise ratio improves, but the quality factor changes due to nonlinear effects
Solution Approach 1:
The system uses feedback to measure the actual quality factor at the operating drive amplitude and uses this information to adjust subsequent drive amplitudes. This ensures that the drive amplitude is optimized for signal strength while maintaining consistent quality factor by compensating for nonlinear effects through continuous adaptation.
Solution Approach 2:
The patent transitions from a static drive amplitude approach to a dynamic one where the drive amplitude is continuously adjusted based on the measured quality factor. This dynamic adjustment allows the system to optimize signal strength while compensating for nonlinear effects that would otherwise cause quality factor variations.
Data Source
AI summary
A circuit comprising a microelectromechanical (MEMS) gyroscope and a gain circuit coupled with the MEMS gyroscope. The gain circuit is configured to receive a digitized drive signal based at least in part on a digitized drive voltage amplitude of the MEMS gyroscope. The gain circuit is also configured to determine a percentage change in quality factor of the MEMS gyroscope based at least in part on the digitized drive signal and a stored trim value of the MEMS gyroscope. The gain circuit is also configured to compensate for an effect of a change in the quality factor of the MEMS gyroscope based at least in part on the percentage change in quality factor.