Quad-band bidirectional metasurface microwave absorber with a patchwork of circular-patch resonators

In this paper, we present a straightforward design of a quad-band bidirectional metasurface microwave absorber (MMA) utilizing circular-patch resonators (CPRs). The MMA is comprised of tri-layer metal CPR structures separated by a dielectric substrate, which achieves perfect absorption due to the fundamental dipolar mode resonance in the CPRs structure. The absorption properties of the MMA can be adjusted by varying the radius of the CPRs structure. Moreover, we have demonstrated that strong absorption of the quad-band bidirectional MMA can be achieved by combining four CPRs with varying radii as a super unit-cell. Our simulation results reveal that the designed quad-band bidirectional MMA exhibits absorbance of 96.4%, 98.2%, 97.6% and 97.1% at 9.08 GHz, 10.07 GHz, 11.39 GHz and 12.95 GHz, respectively, which has been validated through experiments. Furthermore, the quad-band MMA maintains absorption stability under normal forward (+z) incident waves with different polarization angles for both transverse electric (TE) and transverse magnetic (TM) modes. Given its performance characteristics, the quad-band MMA may be an attractive option for potential applications in sensing, detecting, and communication.