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

Radio frequency (RF) micro electro-mechanical systems (MEMS) switches are rapidly replacing the PIN 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 switch with two shunt beams for Ka-band (۲۷-۴۰ GHz) applications such as in communications satellites. Simulation results using Ansoft’s high frequency simulation software (HFSS) at Ka-band shows in the down-state of switch, the isolation (S۲۱) is > ۴۷ dB and return loss (S۱۱) is < ۰.۳ dB. In the up-state, the insertion loss (S۲۱) is less than ۰.۱۵ dB and the return loss (S۱۱) is more than ۱۸ dB. The pull down voltage of designed switch is ۵.۱۳ V and down-state to up-state capacitance ratio (Cd/Cu=۱۲.۱۱pF/۰.۱۳۷pF) is ۸۸.۳۹. Also a novel index material (IM۲) is proposed to determine optimum material using Ashby approach. In this paper the Aluminum (Al) is chosen for the membrane for having low pull down voltage and silicon nitride (Si۳N۴) is chosen for dielectric for having faster switching speed and larger down-state capacitance.

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