Design of High Isolation Ka-band Radio Frequency MEMS Capacitive Shunt Switch

Radio frequency (RF) micro electro-mechanical systems (MEMS) switches are rapidly replacing thePIN diodes and field-effect transistors (FET). Linear behavior, low power consumption, low insertion loss, high isolation, improvement power handling and etc. are benefits of MEMS switches.This paper presents a high isolation RF MEMS capacitive switchwith two shunt beams for Ka-band (27-40 GHz) applications such as in communications satellites and uplink.Simulation results using Ansoft’s high frequency simulation software (HFSS) at Ka-band shows in the down-state of switch, the isolation (S21) is -47 dB and return loss (S11) is -0.3 dB.In the up-state, the insertion loss (S21) is -0.15 dB and the return loss (S11) is -18 dB. Thepulldown voltage of designed switch is 5.13 V and down-state to up-state capacitance ratio(Cd/Cu=12.11pF/0.137pF) is 88.39.Also a novel index material (IM2) is proposed to determine optimum material using Ashby approach. In this paper theAluminum (Al) is chosen for the membrane for having low pull down voltage and silicon nitride (Si3N4) is chosen for dielectric for having faster switching speed and largerdown-state capacitance.