Electromagnetically actuated MEMS microwave switch

The operation of a MEMS microwave switch using a 100-micron-throw electromagnetic actuator is described in this paper. The actuator is fabricated on a steel substrate using an ultra thick photoresist (SU-8). The SU-8 is used as (i) a mould for fabrication of the copper coil and (ii) the actuator core when loaded with a ferromagnetic powder. Electromagnetic actuation results in a force that is up to 100 times greater than that which can typically be obtained electrostatically for the same physical size. Devices with gaps up to 200 microns have demonstrated switching lifetimes of more than 12 million cycles. The switch could be used as an isolator in a microwave circuit where a large switching gap and high contact force are required to provide both high isolation and low transmission loss in the ´open´ and ´closed´ states respectively. The isolation was measured to be 44.5 dB at 10 GHz using a 100 μm break between the signal lines. The insertion loss in the closed state was measured to be 0.41 dB at the same frequency.