Wide tuning-range resonant-frequency control by combining electromechanical softening and hardening springs

This paper presents a device concept for electrostatic resonators utilizing a combination of electromechanically softening and mechanically hardening springs in order to improve tuning capability and reach low values of the resonant frequency. The microscale device was designed for and fabricated in the SOIMUMPS process with a device-layer thickness of 25μm and an active area of 4×5mm
²
. Measurements with base-excitation of the device demonstrate a large tuning range from about 1147Hz down to 120Hz and a maximum relative bandwidth exceeding 100%, e.g. 740Hz.