A highly efficient low-profile tetra-band metasurface absorber for X, Ku, and K band applications

Abstract

This manuscript proposes a highly efficient multiband, low-profile, and single-layered metamaterial absorber (MA). The unit cell of the proposed MA structure is based on split-ring resonators (SRRs) consisting of an outer square-shaped ring, four circular rings, and an inner vectorial-symmetric star shape design, implemented on the cost-effective FR4 substrate. Our proposed MA is highly efficient as it achieves tetra-absorption peaks at f1 = 8.0 GHz, f2 = 13.1 GHz, f3 = 16.08 GHz, and f4 = 19.2 GHz with 99.69%, 99.99%, 97.59%, and 99.99% absorptivity, respectively. The proposed structure is 0.65 mm thick, with 1/58, 1/36, 1/30, and 1/25 of respective free-space wavelengths. The proposed design has a polarization insensitivity (ϕ) up to 90° and an angular stability (θ) up to 70°, owing to the sub-wavelength size and improved cyclic-4 (C4) rotational symmetric structure of the unit cell. To understand the electromagnetic behavior and absorption methodology of the proposed structure, surface current distribution and electric field results have been examined. A prototype MA design was fabricated and tested to validate the performance of the design. Under normal incidence of an electromagnetic (EM) wave, the MA prototype achieves near-perfect absorption at the desired resonant peaks. Variations of θ and ϕ were also examined on the fabricated model and the results found were consistent with the simulated ones.