A 500–750 GHz RF MEMS Waveguide Switch

Abstract

This paper reports on a submillimeter-wave 500-750 GHz MEMS waveguide switch based on a MEMSreconfigurable surface to block/unblock the wave propagation through the waveguide. In the non-blocking state the electromagnetic wave can pass freely through the MEMS-reconfigurable surface while in the blocking state the electric field lines of the TE10 mode are short circuited which blocks the wave propagation through a WM-380 (WR-1.5) waveguide. A detailed design parameter study is carried out to determine the best combination of the number of horizontal bars and vertical columns of the MEMS-reconfigurable surface for achieving a low insertion loss in the non-blocking state and a high isolation in the blocking state for the 500-750 GHz band. Two different switch concepts relying on either an ohmic-contact or a capacitive-contact between the contact cantilevers have been implemented. The measurements of the switch prototypes show a superior RF performance of the capacitive-contact switch. The measured isolation of the capacitive-contact switch designed with 8 µm contact overlap is 19 to 24 dB and the measured insertion loss in the non-blocking state is 2.5 to 3 dB from 500-750 GHz including a 400 µm long micromachined waveguide section. By measuring reference chips, it is shown that the MEMS-reconfigurable surface contributes only to 0.5 to 1 dB of the insertion loss while the rest is attributed to the limited sidewall metal thickness and to the surface roughness of the 400 µm long micromachined waveguide section. Finally, reliability measurements in an uncontrolled laboratory environment on a comb-drive actuator with an actuation voltage of 28 V showed no degradation in the functioning of the actuator over one hundred million cycles. The actuator was also kept in the actuated state for 10 days and showed no sign of failure or deterioration.

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