A Digitally Coded Intelligent Reflecting Surface for 6G Wireless Communication

This paper presents the design of a L-bit digitally coded intelligent reflecting surface based on anomalous reflection properties for sub-6 GHz 6G wireless communications. First, we designed a 1-bit digitally coded PIN-diode loaded unit cell to generate the required phase gradient of 180° between two programmable states. Using this unit-cell, a full RIS (reconfigurable intelligent surface) is synthesized as a square array having aperture size of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$8\lambda_{0}\times 8\lambda_{0}$</tex> (where <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\lambda_{0}$</tex> is the free-space wavelength at 5 GHz). We programmed the RIS for different steering directions and demonstrated the scattering performance using full-wave CST MWS solver, and also validated the performance using fabricated prototype. It is observed that the designed RIS successfully generates beams in the desired directions with an Half-power beam width of 6° respectively, having scan-loss free steering range of 0° - 60°.