Ultrawideband metamaterial absorber covering X- and Ku-bands with a single-layer design

We present a single-layer metamaterial absorber comprising cross-shaped metallic elements embedded within a square-shaped ring and an outer split-ring resonator (SRR) loaded with discrete resistors. The proposed absorber exhibits polarization-insensitive absorption exceeding 90% over a broad frequency range from 7.35 GHz to 18.18 GHz, fully covering the operational requirements of the X – and Ku-bands. Three distinct resonance modes are identified at 7.9, 13.13, and 17.85 GHz, contributing to an effective absorption bandwidth of 10.83 GHz. Furthermore, the absorber maintains stable performance under oblique incidence. A systematic design methodology for configuring metallic resonator layers is proposed to guide metasurface absorber development. A prototype sample is fabricated, and the measured absorptivity is in good agreement with full-wave simulation results. Compared with previously reported metasurface absorbers, the proposed design offers simpler fabrication, broader operating bandwidth, and better suitability for applications requiring strong immunity to electromagnetic interference.