Improved broadband (75–110 GHz) radio frequency characteristics of MEMS shunt switches on quartz substrate

Abstract

This paper presents improved W-band (75–110 GHz) radio frequency characteristics of micro-electromechanical switches in T and π-matched configurations. The switch structures consist of Au metallic bridge (s) suspended over the coplanar waveguide (CPW) signal line drawn on quartz substrate. Here, a high impedance transmission line is introduced on both the sides of the bridge structure to reduce the return loss. To further tune up the broadband RF response the bridge width (40–80 µm) as well the dielectric thickness (0.15–0.18 µm) are varied. At optimum condition (bridge width: 60 µm; dielectric thickness: 0.18 µm), the T-matched RFMEMS switch structure exhibits return loss better than − 20 dB; insertion loss ~ − 0.2 dB and isolation better than − 30 dB in full W-band frequency range. In π-match configuration, a short section of high impedance transmission line is being introduced between two switch structures for impedance matching. RF parameters of the π-matched shunt switch structure are studied as a function of width (10–40 µm) and length (30–180 µm) of the high impedance transmission line. At optimum condition (line width: 30 µm; length: 130 µm), the π-matched switch structure exhibits return loss: better than − 15 dB; insertion loss: better than − 0.5 dB; and isolation: better than − 45 dB over the entire W-band. From the equivalent circuit modeling, the equivalent inductance, capacitance and resistance values for the optimized switch structures are also reported.