A Polarization-Insensitive Frequency Selective Surface Based Rasorber with Narrow-Band Absorption Between Two Transmission Bands

In this paper a Frequency Selective Surface (FSS) based rasorber has been proposed by combining the design of split-ring absorber and dual bandpass FSS on the front and back of a single 0.8 mm thick FR-4 substrate respectively. The proposed rasorber has two transmission windows at around 3.1 GHz and 8.4 GHz with insertion loss of 0.6 dB and 1.2 dB respectively. The transmission corresponds to the bandpass FSS and a resonant absorption at around 6.2 GHz corresponding to the split ring absorber. The parameters of the design are optimized such that at the absorption frequency the bandpass FSS acts as complete metallic ground. The proposed FSS based rasorber also verifies the polarization-insensitive behaviour due to its four-fold symmetry. A prototype of the proposed rasorber is fabricated and the results are experimentally verified.