A Multi-State Reconfigurable Intelligent Surface Based on Anomalous Reflectors for Communication and Radar Applications

We propose a multi-state switchable one-bit digitally coded hybrid metasurface based Reconfigurable Intelligent Surface (RIS), which provides anomalous reflection-based beam steering. The structure consists of both active and passive unit cells periodically arranged to provide different anomalous reflections for different switching states. The proposed RIS is designed to operate at 2.5 GHz, which provides anomalous reflection at <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">± 30∘</tex> under normal incidence when operated in configuration 0000 and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0∘</tex> when operated in configuration 1111. The overall size of the proposed RIS is <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">8λ \ x \ 8λ</tex> (where <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">λ</tex> is free space wavelength at the operating frequency of 2.5 GHz), consisting of 4 clusters of active Unit cells and 4 clusters of Passive Unit cells arranged alternatively to provide anomalous reflection. The biasing lines are further incorporated into the RIS to provide the required voltage to all the P-I-N diodes used in the clusters of the active unit cells. The design of the active and passive Unit cell is four-fold symmetrical, making the structure polarization-insensitive. The proposed RIS can be widely used for beam steering for 6G and beyond, as well as on-Air Mixing applications for potential Doppler Radar spoofing.