A New Finding on Nonlinear Damping and Stiffness of Flexural Mode Capacitive MEMS Resonators

This work reports a new resonant phenomenon of flexural mode capacitive MEMS resonators induced by nonlinear damping and nonlinear stiffness. The measured frequency response clearly demonstrates a variety of interesting resonant behaviors of a capacitive resonator when operated from its linear into nonlinear regime. As the input ac voltage increases (i.e., drive level dependency), the resonant frequency shifts with 6000 ppm while transmission magnitude also varies greater than 200%. Such strong nonlinear phenomenon mainly comes from the flexural mode capacitive resonator featuring excellent electromechanical coupling strength contributed by its narrow transduction gap spacing and large transduction area [1]. A behavior model for predicting nonlinear electrostatic force is built based on the measured linear response under different DC bias. By comparing the simulated result from the behavior model and the actual measurement data, both nonlinear stiffness term and nonlinear damping term can be successfully extracted.