Design of an L-S-Band Frequency Selective Rasorber for Dual-Band Absorption and In-Band Transmission

In this paper, a passive Frequency Selective Rasorber (FSR) for dual-band absorption and in-band transmission operating in the L and S bands is presented. The proposed FSR consists of two lossy Frequency Selective Surface (R-FSS) layers and a lossless FSS layer, with opportune substrates between them for a total thickness of 32 mm. The design procedure of each layer is investigated, and full-wave simulations are performed. The lossy FSSs comprise a modified square loop element loaded with lumped elements. On the other hand, the lossless FSS layer includes a band-pass filter made of a square patch inserted in a connected grid. The simulated results show that the proposed FSR achieves a transmission band from 2.4 to 2.9 GHz with a minimum insertion loss of 1.4 dB. The -10 dB dual-band absorption covers the range from 0.8-1 GHz and from 3.4-3.9 GHz. Furthermore, the presented structure exhibits stable performance against oblique incidences up to 40°.