Square Loop FSS Based Wideband Absorber with High Oblique Incidence Stability

This work presents a frequency selective surface (FSS) based two layer wide band absorber. The top substrate is imprinted with the square loop FSS whereas the bottom substrate is metal backed. The absorber has a thickness of 0.086λL (λL being the wavelength corresponding to the lower cut off frequency). The bandwidth with reflection coefficient below -10 dB is observed from 2.8 GHz to 9.1 GHz (fractional bandwidth (FBW) 106%). The design has a periodicity of 0.14λL and exhibits very stable performance up to 60° angle of incidence. Equivalent circuit model (ECM) based impedance analysis of the absorber is presented to study the underlying principles of absorption.