Ultrawideband Metamaterial Absorber Utilizing Symmetrical Circular Split-Ring Resonator Variants With and Without Extended Cuts for Ku and K-Band Applications

This article presents a cutting-edge broadband metamaterial absorber structure designed for wide-angle incidence across the entire Ku- and partial K-band frequency range. The absorber unit cell comprises a symmetrical circular split-ring resonator and extended arcs from another circular split-ring resonator meticulously designed on an FR4 substrate. After thorough parametric optimization and fabrication, simulation results demonstrate an ultrawideband frequency range from 12.52 to 23.66 GHz, with a 98% absorption rate for normal polarizations. The physical mechanism of the proposed metamaterial absorber structure is elucidated by investigating the distribution of the electric field, surface current, and equivalent circuit model. Furthermore, the absorber's compact size (0.14 $\lambda _{0}$) and cost-effectiveness (FR4 substrate) enable seamless integration into various devices. The novel design strikes a remarkable balance between cost and performance, effectively meeting the stringent requirements of Ku and K-band applications owing to its broad frequency range and outstanding attributes.