X-Band MEMS Capacitive Shunt Switches with Metal-Insulator-Metal Contacts for Improved Isolation

This paper introduces MEMS electrostatically actuated switches that utilize a fixed metal-insulator-metal (MIM) structure for capacitive coupling with a movable shunt bridge to improve the isolation in the off-state. These switches, with single and dual beams, were designed for operation in the X-band frequency range using fixed inductive line section. The advantage of this design is that the isolation, which is directly related to the quality of the capacitive coupling in the actuated state, is not dependent on the planarity of the movable beam structure. Isolations greater than 45 dB and 35 dB at 10 GHz were measured for the double and single beam switches, respectively. From 8 to 12 GHz, an insertion loss of less than 0.3 dB was measured in the on-state for both switch designs. Switching speeds of 40 and 70 mus for the rise and fall times, respectively, of the single beam switch were also measured.