Design of Anomalous Reflectors by Phase Gradient Unit Cell Based Digitally Coded Metasurface

In this letter, we propose the designs of 1-bit and 2-bit digitally coded metasurfaces, which achieve anomalous reflection-based beam-steering. First, we demonstrate the systematic design flow of coded metasurface using phase gradient digital unit cells to achieve anomalous reflection in the preferred direction for a normally incident plane wave. Initially, the design procedure is analytically implemented  to get the phase profiles for 1-bit and 2-bit digitally coded metasurfaces having equal sizes of $10\lambda_0 \times 10\lambda_0$ (where $\lambda_0$ is the free space wavelength at $5.9$ GHz) for a specific reflection angle, $(\theta_r=30^0,\phi_r=0^0)$, and subsequently, the far-field plots are generated. Furthermore, these phase profiles are used to generate 3D-CAD models of the 1-bit and 2-bit metasurfaces using CST, and the desired far-field patterns are obtained having half-power beamwidth (HPBW) of $5^0$. It is observed that the 1-bit coded metasurface produces additional side-lobe levels, which are minimized by use of 2-bit coding. Finally, the proposed 1-bit and 2-bit coded metasurfaces are fabricated, and the anomalously reflected far-field beam is detected by the received power at desired reflection angle and comparing the results with a perfect electric conductor (PEC). The proposed design is suitable for V2X communications and can be scaled to other frequencies.