Low-Profile Anisotropic Metasurface Absorber Enabled by N-Port-Network Inverse Design

Abstract

An N-port-network method is presented for the inverse design of anisotropic metasurface absorbers. Internal discrete ports and four external transverse-electric (TE) and transverse-magnetic (TM) Floquet ports retain angle-dependent reference impedances and co- and cross-polarized responses. The third-generation nondominated sorting genetic algorithm (NSGA-III) searches port states and lumped-element choices. A planar metal-backed absorber with a nominal substrate thickness of 3.2 mm is designed over 5.2–5.9 GHz. Full-wave results satisfy an absorption ratio (AR) of at least 0.8 over approximately 5.24–6.03 GHz for both polarizations at the sampled incidence angles from 0° to 74° in the specified incidence plane. At 5.5 GHz, the incidence-plane azimuth sweep satisfies this threshold at all sampled azimuths up to 50° incidence. A 0.6m×0.6m prototype gives a reflection-derived AR of at least 0.8 over 5.2–5.9 GHz for both polarizations at 7°, 60°, and 75°. These finite-distance measurements are subject to illumination, collection, and normalization uncertainty and do not establish calibrated total absorption at grazing incidence.