A MEMS frequency modulation electrometer based on pre-bias charge mechanism to enhance performance

Abstract

Abstract This paper proposes a prototype of micro-electromechanical frequency modulation electrometers based on pre-bias charge mechanism with a single-anchor circular beam (SACB) resonator. The SACB can overcome the uneven energy distribution in the traditional axial-extended tuning forks structure to weaken the geometric nonlinearity. The charge sensitivity is directly related to the pre-bias charge proven by both theorical and experimental results. With increase of pre-bias charge, the resonator works from the clumsy region to the sensitive region. The SACB electrometer has sensitivity of 5.14 ppm fC−1 under 1.416 pC bias in open-loop measurement and 4.52 ppm fC−1 in closed-loop measurement. Real-time dynamic modulation detection is completed with 0.354 fC step variation. Through the analysis of the noise power spectral density, increasing the pre-bias charge can suppress the noise floor of the resonator. As the bias is increased from 0.708 pC to 1.416 pC, the charge resolution is increased by almost 20 times, and the dynamic range is enlarged by 131%. The pre-bias mechanism can be also used in other resonant sensing applications for improvement of performance.