Polarization-independent symmetrical digital metasurface absorber

Abstract

A metasurface absorber developed using binary-coded unit cells and with the combination of coded unit cells resulted in excellent polarization insensitiveness, symmetrical characteristics, and tunable characteristics. As for binary patterns using the ‘0’ and ‘1’ coded arrangements [00, 01, 10, and 11], ‘1’ position indicates the digital characteristics by high electric and surface current concentration and vice versa for ‘0’. The proposed absorber in this study consisted of a three-layer structure, namely a top metal resonator, an intermediate dielectric layer, and a bottom metallic plane. Structural design, optimization, and result examination of the absorber were performed utilizing the CST microwave studio electromagnetic simulator. Based on the simulated results, absorptance peaks were observed at 11.37 GHz, 15.75 GHz, and 18.76 GHz, whereas the absorptance level were around 97%, 99%, and 94%, respectively. Moreover, the experimented results complied with the simulated results despite slight decreases in absorptance due to cross-polarization effects and free space measurement environments system. The performance of the absorber was also analyzed based on the equivalent medium model theory. Furthermore, the lumped element circuit model of the absorber was explained to verify the simulated resonance of reflection coefficients. The proposed absorber manifested excellent polarization insensitiveness until 45-degree. Meanwhile, the distribution of electromagnetic fields was analyzed to reveal the existence of electro-dipole resonance and magnetic resonance. In conclusion, the performances and diverse characteristics of the binary-coded metasurface absorber were identified to be compatible with integrated micro-circuit devices and encoding information at microwave frequency.