Polarization insensitive U-coupled splits ring resonator-based hexa-band metamaterial absorber for concentration of solid material sensing applications

A U-coupled split ring resonator-based metamaterial absorber (UCSRR-MMA) is presented in this article. The proposed UCSRR's unit cell comprises a fourfold rotationally symmetric structure with a cubic-shaped resonator wrapped in two square rings, which are positioned at every quarter of the MMA. The compact structure is designed with dimensions of 0.2932min x 0.2932min utilizing an FR-4 substrate, where 2 min at the lower absorption frequency. The proposed MMA achieved high absorption of 99.68 %, 95.13 %, 99.88 %, 93.88 %, 99.8 %, and 96.4 % at 8.8 GHz, 10.512 GHz, 13.87 GHz, 16.084 GHz, 22.048 GHz, and 28.348 GHz, respectively, in the X, Ku, K, and Ka-band frequency regions. The absorption characteristics are also investigated using an equivalent circuit model with metamaterial properties, surface current, and electromagnetic field distributions. The permittivity, permeability, and absorption exhibit similar results for both TE and TM polarization modes. Furthermore, this study examines the sensing performance of the UCSRR-MMA with three distinct concentrations of solid mixer: 25 % cement, 40 % cement, and 55 % cement etc. Finally, the effectiveness of the S 11 and absorption characteristics are validated by the fabrication of a physical prototype array. Therefore, the proposed multi-band electrically compact and polarization-insensitive MMA is an attractive candidate for absorption, sensing, and radar cross-section reduction applications.