A Phase Gradient Metasurface for Anomalous Reflection

This paper presents a phase gradient metasurface (PGMS) design to achieve anomalous reflection with an aim for beam steering applications. The basic unit cell topology consists of a square metallic patch printed on a grounded dielectric substrate, whose reflection characteristics (both amplitude and phase) can be varied over a wide range. By tuning the patch length, the reflection phase can be varied over a range of 330°, whereas the return loss is maintained below 0.5 dB at 5 GHz. Firstly, the metasurface is designed by arranging the unit cells with different phase values such that a normally incident electromagnetic (EM) wave undergoes an anomalous reflection towards an angle of 30°. Two different PGMSs are then designed with 1-bit and 3-bit, exhibiting the half power beam widths (HPBWs) of 8.80° and 8.90°, respectively, and directivities of 19.83 dB and 22.00 dB, respectively, in the desired direction of 30°. It is observed that the 3-bit PGMS offers an improved side lobe level (SSL) of-17.08 dB, as compared to that of 1-bit PGMS (having an SLL of -2.98 dB). The 3-bit structure is further studied for different reflection angles (15°, 45°, and 60°) over a frequency range of 4.1 GHz to 5.3 GHz to demonstrate its wideband beam steering feature.