A 14 μHz/√Hz resolution and 32 μHz bias instability MEMS quartz resonant accelerometer with a low-noise oscillating readout circuit.

Abstract

A differential microelectromechanical system (MEMS) quartz resonant accelerometer with a novel oscillating readout circuit is proposed. The phase noise in a piezoelectric quartz resonant accelerometer has been systematically investigated. A high-performance front-end is used to extract the motional charge from a piezoelectric quartz resonator for the first time. This topology eliminates the tradeoff between the gain, bandwidth, and noise of the traditional front-end. The proposed bandpass front-end provides a 14.5 M gain at the oscillation frequency with a phase drift of 0.04°, ensuring a high-quality factor for the quartz resonator. The proposed bandpass front end also achieves input-referred current noise as low as 30.5 fA/√Hz, which helps improve the bias instability and resolution of the accelerometer. An anti-aliasing phase shifter is designed to regulate the loop bandwidth and compensate for additional phase drifts. To reduce the flicker noise introduced by the nonlinear effect, an amplitude limiter is used to set the resonator operating point. The accelerometer achieves a frequency resolution of 14 μHz/√Hz and bias instability of 32 μHz with a ± 70 g full scale, 54.5 Hz/g scale factor, and 552 Hz bandwidth.