Two-bit dual-polarized reconfigurable intelligent surface with low power consumption for 6G near-field communication

Near-field communication using large-scale antenna arrays is one of the hot research topics in the sixth-generation (6G) wireless communication. Reconfigurable intelligent surface (RIS) is a cost-effective method for manipulating electromagnetic waves in the near field. We propose a 2-bit dual-polarized RIS that has the merits of low cost, low power consumption, high phase accuracy, and polarization diversity. Each element consists of an aperture-coupled microstrip patch, two single-pole-four-throw (SP4T) switches, and two groups of microstrip delay lines. Two-bit phase shift is achieved by using only one SP4T switch that controls the connection of four parallel delay branches. Dual polarization is generated by placing two orthogonal slots with two 2-bit phase shifters. A 15×15 RIS prototype operating in the 3.6 GHz band is fabricated and measured. The beam can be scanned in the ±60° range, with a peak aperture efficiency of 40.1% for horizontal polarization and 38.3% for vertical polarization. What is more, the total power consumption of the RIS is merely about 100 mW, which is very attractive for massive deployment in 6G near-field communication.