High Temperature Resistant Ultra-Wideband Rasorber Using Low loss Insulate Tile and Double Lossy Frequency Selective Surface

A frequency-selective rasorber (FSR) with high temperature resistance and an ultra-wideband absorption band below one passband is designed and presented. The FSR is constructed by three functional layers: a insulate tile with low loss for resisting to external high temperature environment, two lossy frequency selective surfaces (FSSs) are applied to broaden absorption bandwidth and a lossless FSS with bandpass characteristic at high frequency. The lossy FSS is an array of square ring with meander-lines and resistors. The lossless FSS is a triple-layer metallic structure printed on two dielectric substrates. Under normal incidence, a -10-dB reflection is obtained from 2.9 GHz to 12.5 GHz with a fractional bandwidth of 124.7%. Meanwhile, a -3-dB transmission is achieved from 16.2 GHz to 18.8 GHz. The minimum insertion loss is only 0.21 dB at 16.8 GHz.