An intensive approach to optimize capacitive type RF MEMS shunt switch

Abstract

Optimization of the RF MEMS switch is essential to enhance its performance characteristics at high frequency Millimeterwave applications. Many optimization techniques have been proposed based on design factors and output responses but not confined with the resonant frequency of RF transmission signal. In this paper, a novel optimization technique is proposed using Multiphysics FEM simulations based on electromagnetic and electromechanical studies. A novel Capacitive type of RF MEMS shunt switch is designed by using iterative meander technique and optimized at the resonant frequency of 41 ​GHz which can efficiently used for millimeter wave applications up to 60 ​GHz. The proposed optimization model which is a novel bottom – up approach consists of intermediate steps for optimization of various layers of switch from substrate to beam. The CPW transmission line with 60/100/60 as G/S/G and having 0.5 ​μm as thickness is considered to allow the frequencies up to 60 ​GHz. The width of the suspended Beam of switch is optimized to obtain up-state capacitance of 37 ​fF which allows the RF signal at 41 ​GHz. Parametric analysis has been carried out to obtain optimized thickness of each layer. Two types of switches other than Fixed – Fixed beam are designed using meandering technique to reduce pull in voltage. Among these the proposed Iterative meander switch shows very low pull in voltage of 1.4 ​V and also shows good return loss of −48.9 ​dB at 41 ​GHz and high isolation of −48.42 ​dB at 38 ​GHz. The proposed switches which are optimized at 41 ​GHz does not contains the perforations and suffers from serious stiction problems at downstate. Hence, perforations are introduced in switch membrane and fabricated using surface micromachining technology. The optimized iterative meander switch shows low pull – in voltage of 1.85 ​V which is closely approximated to the simulated value.