One-time frequency sweep to eliminate IQ coupling in MEMS vibratory gyroscopes

This paper explores the influence of the phase delay resulting from the signal processing circuitry on the IQ coupling characteristics in MEMS vibratory gyroscopes. In the conventional method, the phase delay appears as a phase error in the phase-locked loop (PLL) of the drive-mode oscillation control. A detailed theoretical analysis derives an analytical equation of the IQ coupling about the phase error. Then, a one-time frequency sweep (OTFS) procedure, which acts as an in-situation network analyzer, is proposed to compensate for the phase error by automatically modifying the reference value of the PLL control. Further, the OTFS method is tested using a field-programmable gate array (FPGA) based digital platform on a vibratory micro-machined gyroscope. Experimental results demonstrate that the OTFS method effectively eliminates the unwanted IQ coupling, and the tested gyroscope exhibits a bias instability of 0.75 °hr and an angle random walk (ARW) of 0.06 °/hr at atmosphere.