An Angle-Stable Ultra-Wideband Single-Layer Frequency Selective Surface Absorber

Abstract

An ultra-wideband polarization-insensitive frequency selective surface (FSS) absorber is proposed for S to K-band applications. The absorber comprises two compensation slabs, a lossy FSS layer and a grounded dielectric plate. The FSS unit cell is a combination of a second-order Chinese knot and a cross. To enhance the bandwidth and angular stability of the single-layer FSS absorber, a compensation layer composed of FR4 and polymethyl methacrylate (PMMA) slabs is incorporated. The proposed FSS absorber demonstrates a remarkable absorption rate of over 90% within the frequency range of 3.1–22.1 GHz, exhibiting a fractional bandwidth of 150.8%. Even when subjected to an oblique incidence of 45°, the absorber maintains an 80% absorption rate in the frequency range of 4.4–19.1 GHz for both TE and TM polarizations. The total thickness of the FSS absorber is 0.0848 λL (the wavelength at the lowest cutoff frequency), and only 1.08 times the Rozanov limit. To validate the design, a prototype of the proposed absorber was fabricated and measured. Good agreements were observed between the simulations and measurements.