Resonant Drive Techniques for MEMS: A Comparative Study

Abstract

Electrostatic actuation is popular in microelectromechanical systems (MEMS) because of its many advantages. However, it requires high voltage, typically provided by a power supply and a high voltage amplifier, which is limited in gain. As research interest has shifted to explore higher frequency MEMS, various methods have been proposed to amplify the voltage signal fed into the system by coupling it in series to an LC tank circuit. These methods are based on utilizing the electrical quality factor of an RLC circuit driven at its natural frequency. In this thesis, we analyzed and compared among these three resonant drive techniques. We also compared their performance to a voltage amplifier.

The first resonant drive technique matches electrical and mechanical resonances and activates them simultaneously. The second technique drives the MEMS with a two-frequency signal. One frequency is set equal to the electric resonance, while the sum or difference of the two frequencies is set equal to the mechanical resonance. In the third method, an amplitude-modulated (AM) signal that contains an RF carrier frequency and a baseband frequency is used. The LC circuit is tuned to match the carrier frequency to the electrical resonance, and the baseband frequency is set equal to the mechanical resonance.