Tunable multiband metamaterial absorber with polarization sensitivity via multi-tier strip modifications for millimeter-Wave applications

This paper presents a fully passive and geometrically reconfigurable metamaterial absorber capable of achieving multi-band operation in the 20–40 GHz millimeter-wave range. The proposed design evolves systematically from a polarization-insensitive four-band configuration to polarization-sensitive five- and six-band configurations through multi-tier strip modifications applied to a single-layer metallic pattern. Without relying on active components or multilayer stacking, the absorber enables controlled generation of additional resonances and fine frequency tuning while maintaining a simple and fabrication-friendly geometry. Numerical results demonstrate that the four-band design achieves normalized absorptivity exceeding 96%, whereas the five- and six-band configurations maintain absorptivity levels above 95% and 97%, respectively. Detailed parametric analyses reveal the influence of geometric variations on resonance behavior, and electric and magnetic field as well as surface current distributions are investigated to clarify the underlying absorption mechanisms. Owing to its passive configuration, structural simplicity, and controllable polarization response, the proposed absorber offers a practical solution for millimeter-wave applications including advanced wireless systems and frequency-selective electromagnetic devices.