Parametric Excitation, Amplification, and Tuning of MEMS Folded-Beam Comb Drive Oscillator

This paper proposes a new approach for parametric excitation, parametric amplification, and linear and nonlinear tuning of the folded-beam interdigitated comb drive oscillator. The approach is based on adding a new electrode that generates electrostatic force on the truss and accordingly generates axial stress on the folded beams. Depending on the application, this force can be dc force for resonance frequency tuning or ac force that is used for parametric excitation or amplification. Parametric excitation and amplification are utilized to enhance the effective quality factor of the system; therefore, they are used in sensors where the quality factor is a key parameter in determining their performance. The major advantages of this oscillator over traditional types of parametrically excited microelectromechanical systems (MEMS) oscillators are its ability to suppress nonlinearity and achieve high amplitude of oscillation. Here, the extended Hamilton principle is used to derive the equation of motion of the resonator. Then, an approximate solution is introduced using perturbation method of multiple scales. Finally, the frequency response of the oscillator in four different excitation conditions which are resonance frequency tuning, parametric amplification, parametric resonance, and parametric and forced resonance are presented. The approach presented here has the potential to enhance the performance of several MEMS sensor and actuator devices.