Parametric Analysis of W-BAND RF MEMS SPDT SWITCH

This paper presents the design and optimization of an MEMS (micro-electro-mechanical systems) 3- port single pole double throw switch, which utilizes two shunt capacitive switches in ON and OFF branches respectively. Each shunt switch is designed, optimized and integrated in the SPDT switch for the best output RF performances, low insertion loss and high isolation, in W-band i.e., from 75GHz to 110GHz. The proposed SPDT switch consists of two shunt switching elements one in ON branch and the other in OFF branch each placed at lg/4 distance away from the center of T-junction connected to input CPW signal line to improve isolation and insertion loss. Further I/O VSWR is improved by carrying out stepped impedance matching and chamfering of T-junction. The dimensions of the switch have been optimized using FEM simulation, parametric study and analytical calculations. A maximum isolation of 62dB at 79GHz, minimum insertion of - 0.12dB at 110GHz, return loss better than -7dB at excitation port and better than -10dB in ON or conducting port have been achieved.