A 2D-Programmable and Scalable Reconfigurable Intelligent Surface Remotely Controlled via Digital Infrared Code

Reconfigurable intelligent surfaces (RISs) are promising and relatively low-cost tools for improving signal propagation in wireless communications. A RIS assists a base station (BS) in optimizing the channel and maximizing its capacity by dynamically manipulating the reflected field. Typically, RISs are based on dynamically reconfigurable reflectarrays (RAs), i.e., 2-D arrays of passive patch antennas, individually switchable between two or more reflection phases. The spatial resolution of provided reflected field patterns is governed by the aperture dimensions and the number of patches to meet the requirements of different communication scenarios and environments. Here, we demonstrate a 1 bit RIS for 5 GHz Wi-Fi band made by assembling together multiple independently operating and structurally detached building blocks all powered by the same DC source. Each block contains four separately phase-switchable patch antennas with varactor diodes and a common microcontroller extracting digital control commands from modulated infrared light illuminating the entire RIS. Such distributed light-sensitive controllers grant the possibility of scaling the aperture by adding or removing blocks without redesigning any control circuitry. Moreover, in the proposed RIS a full 2-D phase encoding capability is achieved along with a robust remote infrared control.