A Hybrid Frequency Selective Absorber With Dual-Polarized Wireless Communication and Ultra-Wideband Absorption

Traditional multi-layer frequency selective absorbers (FSAs) with antenna circuit suffer from inter-layer interference, which can adversely affect the in-band frequency bandwidth of wireless communication (fractional bandwidth FBW <20% in literature). In this paper, a circuit design of decoupling between FSA-layer and antenna layer is proposed to solve this problem. The hybrid FSA with antenna circuit achieves in-band wideband dual-polarized transmitting/receiving and ultra-wideband absorption of both in-band and out-of-band. The two circuit layers operate independently, resolving the problems of inter-layer interference of conventional multi-layer FSA with antenna circuit. Additionally, the antenna configuration allows for excitation at the receiving end, providing broadband radiation capability without affecting in-band absorption. A prototype of the proposed structure is fabricated with a low profile of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.22\lambda _{0}$ </tex-math></inline-formula>. Simulated and measured results demonstrate the in-band FBW of 65.06% for wireless communication (2.8–5.5 GHz which is much wider than those reported FSAs with antenna circuit, e.g., FBW<20%) for two polarizations, with isolation less than −15 dB. Furthermore, the structure achieves impressive absorption performance, with radar cross-section reduction (RCSR) of 10 dB from 2.8 to 23 GHz (FBW=156.6%), and stable basic RCSR up to an oblique incidence of 30°.