An ultra-wideband metamaterial absorber (MA) consisting of three layers of resistive ink separated by two layers of polymethacrylimide is proposed. The results of full-wave simulation show that the absorptivity is high up to 95% with a bandwidth ratio of 1:9.73 over the wide frequency range from 4.20 to 40.87 GHz, covering the whole C, X, Ku, K, and Ka bands. Moreover, the MA is insensitive to polarization and exhibits wide-angle stability, which is investigated by the full-wave simulation results as well as the analysis of multi-reflection interference theory. The fabricated prototype with a single unit cell of 0.081 g is tested using free-space measurement in an anechoic chamber, and the measured results are in good agreement with the simulation results, which prove the robustness of the design and indicates a practical application prospect of the proposed ultra-wideband MA with lightweight, simple, and compact structure.

The absorption band in which near-unity or perfect absorption can be realized is still narrow in the current broadband metamaterial absorbers (BMAs). In this article, a broadband perfect metamaterial absorber (BPMA) based on surface plasmon resonance (SPR) is proposed for the visible and near-infrared range. The BPMA composed of a patterned Ti₃C₂T_x layer, SiO₂ layer and the ground gold layer can offer over 90% absorption across the wavelength range of 639–967 nm. It is worth noting that near-unity absorption can be achieved in the range 728–890 nm, which is out of reach by the currently reported BMA. The electric field distribution reveals that localized SPR generated by the Ti₃C₂T_x layer contributes to the broadband perfect absorption. Additionally, the BPMA is insensitive to incident and polarized angles at TE and TM modes. The calculated results based on interference theory agree well with the simulation results, thus supporting the design. This work may provide a potential approach to broadband perfect absorption in the visible and near-infrared region.