Switchable RF MEMS Ka-band frequency-selective surface

A switchable Frequency-Selective Surface (FSS) was developed at 30 GHz using RF MEMS switches on a 500 μm thick glass substrate. For a band-pass filter characteristic, a four-legged loaded element is used with tunable capacitive loading (RF MEMS) and DC-biasing for actuation. The 3" diameter FSS is composed of 909 unit cells and 3,636 MEMS bridges with a reliability of 99.5%. The FSS shows a transmission loss of 2.0 dB and a -3 dB bandwidth of 3.2 GHz at a resonance frequency of 30.2 GHz with the MEMS bridges in up-state position. The -1 dB bandwidth is 1.6 GHz. When the MEMS bridges are actuated to the down-state position, an insertion loss of 27.5 dB is measured. Theory and experiment agree quite well. This is the first demonstration of a switched low-loss FSS at Ka-band frequencies.