Research on the Dynamics and Bistable State of a MEMS Variable Capacitor

With the squeeze film damping, a dynamic model of MEMS two-parallel-plate variable capacitor is established, and numerical solution is derived based on iterative method. Three possible states of suspended plate, which are underdamping, overdamping and pull-in states, are calculated using different structural parameters. Additionally, the relations between the resultant forces and displacements of suspended plate show that with the increase of V_DC there are three similar states when beta is within a certain range. Furthermore, we explain why the bistable state exists in variable capacitor, and work out the values of displacement in stable and metastable state. Finally, the characteristic of bistable state is applied to investigate the tuning range of variable capacitor, and it is found that the tuning range of two-parallel-plate capacitor may be larger than 50% theoretically