Comparison Between Different Designs and Realizations of Anomalous Reflectors for Extreme Deflections

Metasurfaces enable efficient manipulation of electromagnetic radiation. In practice, control over reflection direction is possibly the most useful. Extensive research has been done in the field of anomalous reflectors over the past years, resulting in numerous introduced geometries and several distinct design approaches. Without a comprehensive comparison between design methods, it is difficult to properly select the most appropriate method and the most suitable metasurface geometry. Here, we consider four main approaches that can be used to design anomalous reflectors for large deviations from specular reflection within the same basic structure topology for microwave and millimeter-wave applications. These approaches include the phase-gradient design, which is well-suited for small deviation angles due to its simplicity in design and realization. The second and third approaches involve optimization-based methods at the level of input and grid impedances, respectively. The fourth method is a non-local approach that optimizes supercells of the structure. We analyze and discuss a wide range of performance aspects, such as the power efficiency and losses, angular response, and the scattering pattern of finite-size structures. We believe that our study is particularly interesting for researchers working on metasurfaces, communication technologies, and reconfigurable intelligent surfaces.