Numerical Modeling of Reconfigurable RF MEMS-based Structures Involving the Combination of Electrical and Mechanical Force

Abstract

MEMS are minimized electromechanical devices and systems that are realized using integrated micro fabrication methods. And the technology is growing rapidly in RF field, because of the advantages over p-i-n diode or FET switches. The main application areas of MEMS devices in the future are Information Technology, Bioelectromagnetic, Medical Science. For the accurate design of RF MEMS structures, effective computationally modeling of their transient and steady state behaviors including the accurate analysis of their time-dependent moving boundaries is essential. This is because an accurate knowledge of the electromagnetic field (EM) evolution around a moving or rotating body is very important for the realization of new optical devices or microwave devices, such as the RF-MEMS structures used in phase-shifters, couplers, filters, tuners or antennas. The technique proposed in this paper to model MEMS structures is based on the finite-difference time-domain (FDTD) method with an adaptive implementation of grid generation. Here, this simulation method is applied to the analysis of a two-dimensional MEMS variable capacitor with non-uniform motions, such as accelerated motions. The acceleration of the MEMS capacitor is derived under the equilibrium between the spring force and electrical force. Using this acceleration, the motion characteristic for each time step is derived. The numerical results that express the relationship between the acceleration of the plates and the spring constant and the mass of the plates are shown and the transient effect is accurately modeled.