A Polarization-Insensitive Ultra-Broadband FSS Absorber with Low-Profile Based on the ITO Film

This paper presents a ultra-wideband thin absorber covering the low-frequency microwave band based on frequency selective surfaces (FSS). The proposed FSS absorber consists of three layers of indium tin oxide (ITO) patterned films with dielectric substrate between the films and a metal ground plate. Operating principle of ultra-broadband is analyzed based on the reflection characteristics of each FSS layer and the electromagnetic loss distribution of the structure. The simulation result of the equivalent circuit model (ECM) agrees well with the full-wave simulation. The designed structure has a reflection coefficient of less than -10dB at 1.01 GHz to 18.80 GHz, obtaining a remarkable relative bandwidth of 179.6% while the thickness is only <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.084λL</tex> . The absorber is also able to maintain a stable absorption at large incidence angles for both TE and TM polarized wave incidence.