Waveform design for pulse-and-hold electrostatic actuation in MEMS

Microelectromechanical systems (MEMS) ohmic switches for radio-frequency (RF) signals have certain advantages over solid-state switches, such as lower insertion loss, better linearity, and lower static power dissipation. The RF MEMS switch discussed in this paper consists of a plate, suspended over an actuation pad by four double-cantilever springs. Closing the switch with a step actuation voltage typically causes the plate to rebound from the electrical contacts. This interrupts the signal continuity and degrades the performance, reliability and durability of the switch. This paper presents a procedure to design shaped waveforms to close the switch with low impact speed. The soft landing waveform is designed with a synergy of a three-dimensional finite element model (3-D FEM), a reduced-order model, and experimental refinement with a laser Doppler velocimeter. This integrated approach enables the switch to close with low impact speeds that do not result in significant mechanical rebound.