Eliminating Ground Reliance in Reflective Metasurfaces for Anomalous Reflections.

Reflective metasurfaces (RMs) have gained significant attention in optics and electromagnetism for their ability to redirect signals to customized angles, offering cost- and energy-efficient solutions to line-of-sight (LoS) blockages. However, existing RM technologies predominantly rely on metallic ground planes for efficient beam reflection, which imposes several critical limitations, such as restricted angle range and increased dielectric losses. In this work, we develop an innovative approach that eliminates dependence on metallic ground planes. We introduce an open-edge loop structure as the unit cell, where the gap between the loop edges facilitates phase variation while maintaining high reflectivity. Three distinct yet representative open-edge loop-based RMs were examined under varying incidence and reflection angles. Notably, our developed RMs can function as a "wave bender", the first of its kind, capable of transforming an incident wave into an endfire reflected beam (θ = 90°). They achieve a directivity improvement of around 5 dBi in comparison with conventional ground-based designs. Experimental verification confirms beam reflection at the simulated angles in a wide operating bandwidth from 26 to 33 GHz. This work represents the first demonstration of high-performance beam reflection for RMs without reliance on a metallic ground plane.