Interdigitated resonator based frequency selective rasorber with high selectivity

Abstract This paper investigates a highly selective frequency selective rasorber (FSR) utilizing interdigitated resonators, characterized by a passband exhibiting low insertion loss (IL) and the introduction of a second-order passband response in the lossless layer enhances selectivity on both sides of the passband. The lossy unit is implemented by inserting interdigitated resonators on an octagonal ring loaded with lumped resistors, while the lossless layer is constructed with a five-layer structure. Simulation results demonstrate a low IL value of 0.78 dB at 3.5 GHz. At vertical incidence, the S 21 >−3 dB bandwidth ranges from 3.41 to 3.67 GHz, and the S 11 <−10 dB range spans from 2.2 to 8.2 GHz, obtaining two absorption bands on either side of the passband, with absorption rates exceeding 80%. The operating frequency bands are 1.95–3.27 GHz and 3.8–8.4 GHz. The designed FSR exhibits polarization insensitive. To validate simulation results, a prototype FSR was fabricated and tested, with experimental data aligning with simulation results.