A 2:1 Bandwidth 3-6 GHz Dual-Polarized True-Time-Delay Based Reconfigurable Intelligent Surface (RIS)

This paper presents a 144 -element 3-6 GHz dual-polarized true-time-delay (TTD) reconfigurable intelligent surface (RIS). The RIS employs commercial SP4T RF switches and TTD lines to accomplish wideband phase shift and beam steering. A stacked patch antenna is designed as the unit element on a low-cost printed circuit board (PCB), and an optimization algorithm is used to determine the optimal phase shifter distribution across the array aperture. The RIS demonstrates <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\pm 60^{\circ}$</tex> scanning capability and EVM >2% for all scan angles at 3-6 GHz using a 400 MHz 64-QAM waveform, enhancing network conditions in the high FR1 band and supporting multi-standard operations. To the author's knowledge, this work shows the first wideband RIS that supports octave bandwidth.