An Energy-Autonomous Reconfigurable Surface with Dual-Polarized Unit Cells for Simultaneous Beam Steering and Energy Harvesting

This paper introduces the design of a new energetically self-sustained 10× 10 reconfigurable intelligent surface (RIS), operating in the 2.4 GHz band. The metasurface unit cell (UC) consists of a two-port planar patch capable of receiving dual-polarized waves. Reconfigurable steering of the vertical incident wave is enabled by tuning an ultra-low-power varactor, while the horizontal component drives a rectifier supplying the required DC bias. A compact layout is achieved by connecting the UC ports to their nonlinear loads through back-plane via-holes. First, the UC is designed through nonlinear/electromagnetic (NL/EM) co-simulations, including its layout and nonlinear terminations. Then, the full 10×10 metasurface is configured under different varactor biasing conditions to achieve the desired reconfiguration. The rectifying networks, organized in columns and in voltage multiplier connection, achieve a maximum DC output voltage and power of 3.5V and 340μW, respectively per column. The self-sustained RIS is capable of reflecting the vertically polarized incident wave within a desired angular range from -40° to 40°, achieved by tuning the varactor bias voltage in the -10 ÷ 0V range.