Wave-Controlled RIS as Reconfigurable Reflective Lens for Focusing in the Fresnel Zone

We propose a reconfigurable metasurface-based lens that employs a novel method for biasing the varactors and reflecting incident rays at a desired focal point. The reconfig-urable intelligent surface (RIS) uses resonant standing waves on a biasing transmission line (TL) below the RF reflective surface. This novel biasing technique eliminates the need for separate external bias for each RIS element. We use an analytical RIS model to obtain the electric field distribution at the focal plane.