Modeling and Control of Electrostatically Actuated RF-MEMS Switches

Abstract

This work presents a novel approach to modeling and control of an RF- MEMS switch. The model presented in this work is comprehensive and generic in nature such that it takes into account the effect of squeeze film damping, impact force and electrostatic force effects on the dynamic behavior of the switch during pull-in and release of its membrane. This model makes it adaptable to any similar switch regardless of the form and/or dimensions. Simulation results of the switch dynamics is validated against experimental data for an identical switch. Model response to electrostatic voltage shows very good agreement with experiments. The proposed model is then used to construct a feedback controller capable of improving response parameters of the membrane during operation. Due to micro-dimensions of the switch, real time displacement measurement of the membrane is not readily available. Therefore, the proposed controller utilizes measurement of switch capacitors current as a platform for real time estimates of the membrane position. Membrane Current measurement was not available for control purposes due to the lack of the fabricated RF MEMS switch. Consequently, approximate model for current-displacement relationship is constructed from numerical solution of the nonlinear model data and system identification techniques using Simulink.