A Dual-Polarized Wideband Frequency-Selective Rasorber in Absorption-Transmission Configuration for S-C Bands

This paper presents a passive dual-polarized Frequency Selective Rasorber (FSR) in an Absorption-Transmission configuration, covering S and C bands. The proposed FSR consists of an absorbing resistive Frequency Selective Surface (FSS) operating together with a wideband transmitting lossless FSS. The design methodology for each layer is thoroughly analyzed, and full-wave simulations are performed to verify the performance. In details, the absorbing FSS includes two layers, etched on both sides of a 0.5 mm thick FR4 dielectric substrate. The two lossy layers are perpendicularly positioned on their respective side to cover both TE and TM polarizations, featuring a meandered square spiral arm unit cell, loaded with opportune resistors. On the other hand, the wideband bandpass filter is designed by placing a 0.5 mm thick FR4 dielectric substrate between two lossless FSS layers. These FSS layers are mutually perpendicular to consider various polarizations and are implemented as an I-shaped unit cell. Simulation results demonstrate that the proposed FSR achieves a -3 dB transmission band ranging from 2.9 to 7.05 GHz, corresponding to an 83.4% fractional bandwidth, with a minimum insertion loss of -0.75 dB. The -10 dB absorption band spans from 1.55 to 2.9 GHz, resulting in 63 % fractional absorption bandwidth. Additionally, the structure shows stable performance for oblique incidences up to 30° and a considerably reduced overall thickness, i.e. 31 mm (i.e. <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\lambda_{L}/5)$</tex>.