Improving controllability in RF-MEMS switches using resistive damping

Abstract

An efficient way to control the impact velocity in order to achieve soft landing and fewer bouncing phenomena is the resistive damping. This control method is also referred as charge drive and presented for first time by Castaner and Senturia [1]. Under charge control the Pull-in phenomenon of the Constant Voltage controlled electrostatic actuators does not exist and if the current drive is ideal, any position across the gap is stable. The main reason for this behavior is that the electrostatic force applied is always attractive and independent of the remaining gap of the actuator. Charge drive control incorporating constant current sources is mostly preferred to extend the travel range of electrostatic micro-actuators [2], [3], [4], [5]. Nevertheless there are very few references in the literature about charge drive control on RF MEMS. Recently published work based on numerical simulations for capacitive RF-MEMS, [6] and [7] present a learning algorithm in order to reduce fabrication variability using resistive damping for the pull-down phase. Nevertheless none of them present any details on how to implement resistive damping and any results of such kind of applications. This work presents in detail the entire procedure in calculating the bias resistance of an RFMEMS switch controlled under resistive damping.