A Piezo-Capacitive High-Frequency Resonant Accelerometer

In this work a frequency-modulated (FM) resonant accelerometer operating based on the piezoelectric stiffening effect is introduced for the first time. In this device, the acceleration-sensitive variation of a capacitive mass-spring (CMS) system is up converted to a carrier frequency which is set by the resonance frequency of a thin-film piezoelectric-on-silicon (TPoS) resonator due to the piezoelectric stiffening effect. The mechanical decoupling of the acceleration-sensitive component from the resonant component allows for an additional degree of freedom in the design and a larger dynamic range, while enabling high frequency operation of the accelerometer. Proof-of-concept Z-axis accelerometers at ~27 MHz are presented with an acceleration sensitivity of ~300 Hz/g, The acceleration/axis sensitivity is mainly dependent on the design of the CMS and ultimately limited by the effective electromechanical coupling of the TPoS resonator.