Single-layer six-band metasurface absorber for microwave applications.

A single-layer six-band metasurface absorber for microwave applications is presented, fabricated, and experimentally validated. The proposed unit cell is composed of concentric inner and outer ring resonators, with four symmetrically placed stubs on the outer ring at 90° intervals. The structure is printed on a 2.4 mm thick FR4 substrate with a loss tangent of 0.02 and backed by a continuous metallic ground plane. The novelty of the design lies in achieving six distinct absorption bands using a simple single-layer ring-based geometry, without requiring multilayer stacking or additional lumped components. The absorber operates over the frequency ranges of 2.278-2.317 GHz, 4.496-4.571 GHz, 10.44-10.59 GHz, 13.518-13.65 GHz, 14.66-14.82 GHz, and 17.77-18.70 GHz. A comparatively wide absorption bandwidth of 930 MHz is obtained in the highest-frequency band. The absorption magnitude remains above 90% across all six operating bands. The absorption mechanism is investigated through surface impedance matching, C4-symmetric current cancellation, and surface current distribution analysis, showing that the lower bands are mainly associated with magnetic resonances, while the higher bands originate from electric and hybrid resonant modes. The simulated and measured results show good agreement, confirming the effectiveness of the proposed metasurface absorber for multiband microwave absorption applications.