A Dual-Functional Frequency-Selective Rabsorber with Linear-to-Circular Polarization Conversion and Out-of-Band Absorption

This paper proposes a novel frequency-selective rabsorber (FSR) integrated with a receiver-transmitter metasurface (RTMS) to achieve both out-of-band electromagnetic stealth and in-band polarization conversion. Unlike conventional FSR designs that rely on bandpass frequency-selective surfaces (FSS), the proposed structure replaces the bandpass FSS with an RTMS layer, enabling mutual polarization conversion between x-polarized and right-hand circular polarized (RHCP) waves. Simulation results confirm that the proposed structure maintains |S<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</inf>| below -10 dB over a wide out-of-band range (2.7-8.5 GHz), demonstrating strong absorption of out-of-band waves. Within the operational band (4.6-5 GHz), |S<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</inf>|<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">(RCP-X)</inf> exceed -2.5 dB, demonstrating efficient linear-to-circular (LTC) polarization conversion with minimal transmission loss. Therefore, this structure achieves dual-function performance, offering both polarization conversion and absorption-transmission-absorption (A-T-A) mechanism, making it highly suitable for applications in 6G communication and radar stealth technology.