Design of Readout Circuit with Quadrature Error and Auxiliary PLL for MEMS Vibratory Gyroscope
Smart Sensing Center, Institute of Microelectronics, Chinese Academy of Sciences, Beijing 100029, China
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Author to whom correspondence should be addressed.
Sensors 2020, 20(16), 4564; https://doi.org/10.3390/s20164564
Received: 8 July 2020
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Revised: 11 August 2020
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Accepted: 12 August 2020
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Published: 14 August 2020
(This article belongs to the Collection Inertial Sensors and Applications)
Traditional MEMS gyroscope readout eliminates quadrature error and relies on the phase relationship between the drive displacement and the Coriolis position to accomplish a coherent demodulation. This scheme shows some risk, especially for a mode-matching gyro. If only a slight resonant frequency deviation between the drive and sense mode occurs, a dramatic change in the phase relationship follows, which leads to a wrong demodulation. To solve this, this paper proposes a new readout based on the quadrature error and an auxiliary phase-locked loop (PLL). By tuning the phase shifter in the sense-mode circuit, letting the quadrature error and the carrier of the mixer be in 90° phase alignment, the Coriolis was simultaneously in phase with the carrier. Hence, the demodulation was accomplished. The carrier comes from the PLL output of the drive-mode circuit due to its low jitter and independence of the work mode of the gyro. Moreover, an auxiliary PLL is used to filter the quadrature error to enhance the phase alignment accuracy. Through an elaborate design, a printed circuit board was used to verify the proposed idea. The experimental results show the readout circuit functioned well. The scale factor of the gyro was 6.8 mV/°/s, and the bias instability was 204°/h.
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Keywords:
coherent demodulation; quadrature error; phase alignment; phase-locked loop (PLL); MEMS gyro; vibratory gyroscopes; MEMS sensors
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MDPI and ACS Style
Chen, H.; Zhong, Y. Design of Readout Circuit with Quadrature Error and Auxiliary PLL for MEMS Vibratory Gyroscope. Sensors 2020, 20, 4564. https://doi.org/10.3390/s20164564
AMA Style
Chen H, Zhong Y. Design of Readout Circuit with Quadrature Error and Auxiliary PLL for MEMS Vibratory Gyroscope. Sensors. 2020; 20(16):4564. https://doi.org/10.3390/s20164564
Chicago/Turabian StyleChen, Hua, and Yanqing Zhong. 2020. "Design of Readout Circuit with Quadrature Error and Auxiliary PLL for MEMS Vibratory Gyroscope" Sensors 20, no. 16: 4564. https://doi.org/10.3390/s20164564
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