Design and Characterization of an Ultra-Thin Highly Compact Metasurface Absorber for Octaband Electromagnetic Shielding

An ultra-thin and highly miniaturized octaband metasurface absorber, the most compact reported, is proposed for multiband electromagnetic shielding below 12 GHz, implemented on a low-loss substrate (\tan\delta = 0.003). The design is based only on a single 8 \times 8\;\rmmm^2 unit-cell with a thickness of 1.52 mm (0.015\lambda_0). Eight resonant absorption peaks with efficiencies exceeding 95% are achieved through the synergistic interaction of coupled subwavelength resonators, via-loaded current extraction, and a slotted ground plane. The metasurface exhibits quasi-polarization-insensitive under TE and partially under TM up to ± 40°. Free-space (X-band waveguide) measurements on a finite (single) unit-cell array prototype validate the full-wave simulations, showing octaband absorption with close spectral agreement. To further characterize its transmission-suppression and shielding behavior, two-horn free-space transmission measurements under normal incidence were performed and evaluated against a free-space reference. The combination of extreme compactness, high multiband density, and angular robustness makes the proposed metasurface a promising platform for advanced EM field management.