Extraction of Modal Parameters of Micromachined Resonators in Higher Modes

Abstract

In this paper, a micro machined resonator is fabricated using SOI MUMPs process. A total of 50 out-of-plane mode shapes and their corresponding modal parameters (resonant frequency and damping) are extracted. With the applied voltage, due to joule heating, natural frequency (f n ) and Quality (Q) factor change. This can be effectively used for tuning the resonator. A detailed modal analysis is carried out using an FEM simulator to compute the modal parameters across all the modes and results are within 5% of the data measured using a Laser Vibrometer. Q is estimated using the half-power point approach for the first 42 modes. It is also observed that Q goes up by a factor > 2 for modes beyond 27, as only a portion of the structure contributes to modal displacement. At higher voltages, thermal softening is observed due to local heating which results in structure behaving like a coupled resonator. Under these conditions, peak splitting is observed. This structure can be used in different sensor and actuator applications depending on the mode of operation.