A Suboptimal Approach to Huygens' Metasurfaces for Wide-Angle Refraction

Abstract

Huygens' metasurface uses boundary conditions to solve for the required electric and magnetic current densities to provide a theoretical solution for wavefront shaping. However, the physical implementation of Huygens' metasurface often suffers from interlayer coupling, leading to the difficulty in synthesizing the desired properties. This article proposes a novel approach to suppress interlayer coupling using a symmetric wire-loop topology. The proposed unit cell is designed to induce orthogonal components of Huygens' dipole to each face, and the multipole moments are directly calculated from current distributions induced on metallic patterns. Due to the suppressed interlayer coupling, electric and magnetic dipoles can be independently tuned to achieve the desired phase conditions without causing any distortion of electromagnetic responses in their combined structure. Furthermore, the tolerance to the phase difference between dipole moments is analyzed to extend the range of phase gradient for a transmit wave while maintaining high transmit efficiency. The proposed approach is validated by designing two metasurfaces for normally incident waves to bend toward different angles at 10 GHz, and their characteristics are demonstrated by near- and far-field measurements. The measured results confirm that a high transmittance of greater than 83% is achieved up to the maximum validation angle of 65 degrees.