Design and Experimental Performance Evaluation of a Single-Layer Polarization-Insensitive Asymmetric Microwave Metasurface Absorber

This work reports on designing and experimentally evaluating an asymmetric metasurface absorber (MA) for wideband and polarization-insensitive operation in the C- and partial X-bands. As the core building block of the radio frequency (RF) subsystem, a unit cell has been proposed, comprised of a dual-cut square-ring resonator (SRR) and a square patch placed above an FR4 substrate backed by a copper plate, inherently anisotropic. This arrangement efficiently converts linearly polarized waves to cross-polarized reflected waves, achieving an 80% conversion efficiency over a wide bandwidth (BW) of 4.72-8.49 GHz. The reflected cross-polarized waves are also inhibited by strategically incorporating just three resistors on the top surface. Therefore, the polarization converter (PC) is transformed into an MA. In contrast to previously known MAs that depended on structural symmetry to maintain stable absorption performances across all polarization angles, this newly proposed asymmetric MA breaks that constraint. It achieves consistent absorption irrespective of variations in the polarization angle of the normal incident waves. The full-wave simulations have resulted in over 80% absorption, closely resembling the initial PC's reflected BW. This MA has a compact assembly with a size of 0.22 lambda x 0.22 lambda and a thickness of 0.07 lambda . Absorption outputs are experimentally evaluated, resulting in more than 80% absorption, covering almost the entire C-band. This device can be used in different applications, such as radar cross section (RCS) assessments and energy-harvesting front ends.