Wide-angle optimization method for metamaterial absorber structures

Metamaterial absorbers play an important role in various applications such as radar cross-sectional reduction, electromagnetic interference suppression, and stealth technology. However, the absorption performance of many existing metamaterial absorbers decreases significantly with the increase of incident angle due to the distinct variational trends of the characteristic impedance in free space under different polarizations, compared to the input impedance of the absorber structures. Here, we propose a method to improve the oblique incidence performance of metamaterial absorber by loading an additional transmissive layer structure. This structure consists of two periodic layers separated by an air spacer. Simulation results show that the proposed metamaterial absorber has improved oblique incidence absorption performance and stabilized absorption frequency. The absorptivity remains above 87% under TE polarization, as the incident angle increases from 0° to 85°. The method is validated by experiments, and the measured results agree well with numerical simulations. This work presents a simplified and effective methodology to reduce the complexity of designing absorbers with large angles of incidence.