A 2-Bit Programmable Reflectarray Antenna Based on a Polarization-Insensitive Metasurface

In this paper, a programmable reflectarray antenna (PRA) for 5G network in S-band is proposed. The first 2-bit reconfigurable polarization-insensitive metasurface with two substrates, three metal layers and only four p-i-n diodes in each unit cell is developed. The top layer of the proposed unit cell is a slotted polygon patch around with two pairs of p-i-n diodes integrated orthogonally. The 2-bit reflection phase correction is obtained by switching the four ON-OFF states of the corresponding pair of p-i-n diodes. The square-ring slot and vertical slot on the polygon patch is proposed to suppress the cross-polarization level (XPL), which is the bottleneck problem of realizing the polarization-insensitive unit cell with 2-bit phase correction. A prototype PRA with 12 × 12 unit cells is designed, fabricated, and tested. The measurements are in good agreement with expectations and full-wave simulations. The proposed PRA has the capability of two-dimensional (2-D) beam steering within 60° with the maximum aperture efficiency of 31.20% at 3.5 GHz. The proposed reflectarray has the advantages of simple structure, minimum number of p-i-n diodes, high aperture efficiency and polarization insensitivity.