Design and analysis of asymmetric structure capacitive RF MEMS shunt switch

Abstract

This paper deals with the study of shunt capacitive RF switches. Comparative study is done on non-uniform designed structures, which are simulated using finite element modelling and HFSS tools. Asymmetric cantilever structures designed along with perforations to achieve less spring constant, low pull in voltage, and isolation performance in OFF state. Asymmetric cantilever structure shows low pull in voltage of 4.1 V for the left cantilever with low spring constant of 0.84 N/m. Right cantilever has a pull in voltage of 4.5 V with a spring constant of 0.86 N/m. The material used on either side of cantilever is gold with the young modulus of 79 GPa. When the RF gap between the cantilever and dielectric is 1.8 um, the capacitance in the up state is 50 fF and in the down state is 4.1 pF for HfO2. Asymmetric cantilever structure has less switching time of 53.2 ns. By using ANSYS HFSS Electromagnetic analysis is done and observed that a high isolation of − 55 dB at 25 GHz is obtained, when both the cantilevers are deforming downwards. The presented asymmetric cantilever switch tunes the isolation between Ku and K bands, − 48, − 50 and − 55 dB at the frequency ranges of 18, 21 and 25 GHz when the left, right and both cantilevers are in OFF-state. The proposed switch has the insertion loss below − 0.05 dB and the return loss has been obtained below − 55 dB over the frequency range of 1–30 GHz.