Enhancing oblique incidence performance of mm-wave substrate-integrated FSS absorbers

This article proposes a scan compensation approach employing a superstrate and metallic vias to enhance the oblique incidence performance of millimeter-wave (mm-wave) absorbers. The design features a top resistive surface of tantalum nitride (TaN) printed on a gold-backed alumina substrate, achieving a broad absorption bandwidth from 70 to 117.6 GHz (FBW = 50.7%) with a reflection coefficient (Formula presented.), below −10 dB. An equivalent circuit model (ECM) is used to analyze the performance of the designed absorber at oblique incidence angles. The scan compensation approach is introduced based on an analytically optimized cost function, and its integration with metallic vias is investigated to further stabilize oblique incidence absorption. The proposed analytical method can be applied to any general frequency-selective surface (FSS) to improve angular stability.