Noise behaviors of a closed-loop micro-electromechanical system capacitive accelerometer

Abstract

The noise of closed loop micro-electromechanical systems (MEMS) capacitive accelerometer is treated as one of the significant performance specifications. Traditional optimization of noise performance often focuses on designing large capacitive sensitivity accelerometer and applying closed loop structure to shape total noise, but different noise sources in closed loop and their behaviors at low frequencies are seldom carefully studied, especially their behaviors with different electronic parameters. In this work, a thorough noise analysis is established focusing on the four noise sources transfer functions near 0 Hz with simplified electronic parameters in closed loop, and it is found that the total electronic noise equivalent acceleration varies differently at different frequency points, such that the noise spectrum shape at low frequencies can be altered from 1/f noise-like shape to flat spectrum shape. The bias instability changes as a consequence. With appropriate parameters settings, the 670 Hz resonant frequency accelerometer can reach resolution of $2.6 \mu g/\sqrt {Hz}$ at 2 Hz and 6 μg bias instability, and 1300 Hz accelerometer can achieve $5 \mu g/\sqrt {Hz}$ at 2 Hz and 31 μg bias instability. Both accelerometers have flat spectrum profile from 2 Hz to 15 Hz.