A smart millimeter-wave base station for 6G application based on programmable metasurface

The evolution of programmable metasurfaces has yielded many exciting electromagnetic (EM) phenomena and applications in both communities of physical and information sciences. Programmable metasurfaces, also known as reconfigurable intelligent surfaces or intelligent reflecting surfaces in wireless communications, have played important roles in enhancing signal coverage and transmission quality, and in building an artificially controlled communication environment. However, most of the realistic implementations are designed in the sub-6G band with a small array scale and 1-bit phase control ability, making the performance improvement not marvelous compared with the traditional solutions. Here, we propose a large-scale 2-bit millimeter-wave programmable metasurface to build an integrated smart base station framework for 6G communications. The meta-array is composed of 30 x 30 meta-elements, each with two embedded positive-intrinsic-negative (PIN) diodes. A dish-cone antenna is integrated with the metasurface to serve as the feeding source. A control board is designed to autonomously switch the working states of all of the 1800 PIN diodes based on a field-programmable gate array, enabling the individual adjustment of the EM responses of all meta-elements in the array. Through the deliberate arrangement of phase distribution on the surface, the array can undergo reconfiguration to achieve the desired EM functionalities. We take the programmable metasurface as the core to assist a millimeter-wave base station and validate its good performance for wireless communications in a realistic indoor scenario. Subsequently, we build a four-stream wireless communication scenario using four 30 x 30 arrays and demonstrate smart multi-user information transmissions with different positions. This work provides great potential for programmable metasurfaces to aid the development of novel and intelligent millimeter-wave base stations, offering valuable insights for advancing next-generation mobile communications. A comprehensive, large-scale 2-bit millimeter-wave programmable metasurface system for smart base-station applications with precise and wide 2D beamforming characteristics.