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

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.

Automated summary

This letter presents and investigates a polarization-insensitive frequency-selective absorber (FSR) with wideband absorption and in-band transmission characteristics. The proposed FSR consists of one lossy and one lossless resonator, both printed on FR4 substrates and separated by an air spacer. Resistive ink patterns are deposited in the top lossy layer to achieve wideband absorption, improving upon existing FSR structures. The absorptions are observed in the frequency ranges of 1.31-3.22 GHz and 4.88-6.69 GHz, with fractional bandwidths of 84.32% and 31.28% respectively. The bottom lossless layer enables in-band transmission response at 4.05 GHz between the two absorption bands with minimal insertion loss. The proposed FSR is polarization-insensitive and angularly stable, and its design has been validated through fabrication and measurement.