A dual-mass fully decoupled MEMS gyroscope with wide bandwidth and high linearity

A fully decoupled z-axis MEMS gyroscope with wide bandwidth and high linearity is presented in this paper. The mechanical structure consists of a dual proof mass, which are mechanically coupled together using a pair of double folded springs. The fully decoupled approach is employed to lower the mechanical cross coupling between the drive mode and sense mode. The gyroscope is fabricated using a simple two-mask process based on a silicon-on-insulator (SOI) substrate with a 30-μm-thick device layer. The electrostatic actuation and capacitive sensing gaps of around 1.1-μm provide an aspect ratio of close to 27. The narrow capacitive gap increases the electromechanical coupling and improves the signal to noise ratio (SNR) of the sensor. The fabricated MEMS gyroscope is vacuum packaged in a ceramic chip carrier in order to minimize the Brownian noise floor for achieving a better performance. A off-the-shelf integrated circuit with the excitation and sensing electronics is hybrid connected to the gyroscope. The MEMS gyroscope system demonstrates a bias instability of 9.6 deg/h, an angular random walk (ARW) of 0.45 deg/h, a bandwidth of greater than 120 Hz, and a scale-factor nonlinearity of 770 ppm in a full scale range of ±500 deg/s at room temperature.