A frequency-selective rasorber with wideband absorption and in-band transmission using resistive ink

Abstract

A polarization-insensitive frequency-selective rasorber (FSR) with wideband absorption and in-band transmission characteristics has been presented and investigated in this letter. The unit cell of the proposed FSR comprises one lossy and one lossless resonator, both printed on FR4 substrates and segregated by an air spacer. Resistive ink patterns are deposited in the top lossy layer to realize a wideband absorption, displaying significant improvement over the existing FSR structures. The absorption bandwidths are obtained from 1.31 to 3.22 GHz and 4.88 to 6.69 GHz having fractional bandwidths of 84.32% and 31.28%, respectively. An in-band transmission response is occurred, due to the bottom lossless layer, at 4.05 GHz between the two absorption bands with a small insertion loss. The equivalent circuit model is used to develop the proposed FSR and the design variables are formulated accordingly to generate the desired passband and stopband characteristics. Variation in the incident and reflected/transmitted wave properties have also been studied and the topology is found to be polarization-insensitive as well as angularly stable. Finally, the structure has been fabricated and measured to validate the FSR design principle and its performance. © 2022 Wiley Periodicals LLC.