Switchable low-loss RF MEMS Ka-band frequency-selective surface

A switchable frequency-selective surface (FSS) was developed at 30 GHz using RF microelectromechanical systems (MEMS) switches on a 500-μm-thick glass substrate. The 3-in-diameter FSS is composed of 909 unit cells and 3636 MEMS bridges with a yield of 99.5%. The single-pole FSS shows a transmission loss of 2.0 dB and a -3-dB bandwidth of 3.2 GHz at a resonant frequency of 30.2 GHz with the MEMS bridges in the 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. The power handling is limited to approximately 25 W with passive air cooling and >150 W with active air cooling due to the increased temperature of the overall circuit resulting from the transmission loss (for continuous-wave operation with the assumed maximum allowable temperature of 80°C), or 370 W-3.5 kW due to self-actuation of the RF MEMS bridges (for pulsed incident power). Experimental results validate that 20 W of continuous-wave power can be transferred by the RF MEMS FSS with no change in the frequency response. This is the first demonstration of a switched low-loss FSS at Ka-band frequencies.