  Reconfigurable Intelligent Surfaces (RISs) are promising and relatively
low-cost tools for improving signal propagation in wireless communications. An
RIS assists a base station in optimizing the channel and maximizing its
capacity by dynamically manipulating with reflected field. Typically, RISs are
based on dynamically reconfigurable reflectarrays, i.e. two-dimensional arrays
of passive patch antennas, individually switchable between two or more
reflection phases. Different communication scenarios and environments require
RISs to provide a different spatial resolution of reflected field patterns,
which depends on the aperture dimensions and the number of patches. Here we
demonstrate a 1-bit RIS for 5-GHz Wi-Fi band made by assembling together
multiple independently operating 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 re-designing any control
circuitry. Moreover, in the proposed RIS a full 2D phase encoding capability is
achieved along with a robust remote infrared control.
