Broadband Absorptive Frequency Selective Rasorber With Unidirectional Transmission Window

A novel broadband frequency selective rasorber (FSR) with unidirectional transmission window is investigated. It is designed to transmit y-polarized waves with polarization conversion along the +z direction, while simultaneously absorb y-polarized waves across a wide frequency band along the -z direction. The FSR is a composite structure consisting of an upper lossy layer and a lower absorptive transmission-reflection surface (ATRS). The upper layer incorporates two concentric square resonators and four lumped resistors to enable absorption across both low- and high-frequency bands. The ATRS is comprised of three metallic layers, with upper and lower layers consisting of triangle patches connected by a via. A cross slot is etched on the top patch, and three lumped resistors are integrated to facilitate absorption at middle-frequency band. The proposed FSR achieves a wide absorption band in 4.28-25.65 GHz (142.8%) and a wide polarization-conversion transmission band (|S<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">21</inf>|> -3dB) within the range of 14.47-22.53 GHz (43.57%) according to simulation results.