Unloaded wires-based simple biasing circuit for varactor-controlled metasurfaces

This paper introduces a varactor-loaded reconfigurable metasurface designed for discrete beam steering, a feature crucial for many applications such as smart radio environments. Initially, MATLAB is used to determine the meta-atom impedances that yield the desired reflection under normal incidence. Subsequently, capacitive-type meta-atoms are employed to achieve these impedances, which are then replaced with varactor diodes to create the reconfigurable metasurface. The unloaded wires are deliberately integrated into the same plane as the capacitively loaded meta-atoms to serve as biasing wires, allowing for changes in the capacitance of varactor diodes. This approach simplifies the design by eliminating the need for additional substrates for biasing circuitry. The proposed technique is tested on a two-bit reflective metasurface at 10 GHz and demonstrates promising beam- steering performance. The simulated results are confirmed by fabricating and testing the metasurface at different reflection angles.