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

Abstract

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 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$10\lambda _{0} \times 10\lambda _{0}$</tex-math></inline-formula> (where <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\lambda _{0}$</tex-math></inline-formula> is the free space wavelength at 5.9 GHz) for a specific reflection angle, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$(\theta _{r}=30^{0},\phi _{r}=0^{0})$</tex-math></inline-formula> , 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 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$5^{0}$</tex-math></inline-formula> . 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.