Implementation of RIS Beam-Scanning Testbed and Performance Analysis in mmWave OFDM Systems

Reconfigurable Intelligent Surfaces (RIS) offer a low-power, programmable means to manipulate mmWave propagation by dynamically adjusting the phase of an array of passive elements. In this work, we develop and evaluate a 1-bit, 32×32 PIN-diode RIS equipped with an FPGA-based high-speed control board. We implement a codebook-based beam-scanning structure using a LabVIEW host and FPGA for rapid beam switching. We validate beam-steering performance using horn antennas and vector network analyzer, demonstrating precise near-and far-field pattern controls that closely match MATLAB simulations. Finally, we develop a LabVIEW-based 28 GHz end-to-end OFDM testbed and conduct link experiments, showing significant improvements in constellation quality and bit-error-rate (BER) under target beam conditions compared to non-focused conditions. These results confirm that RIS can effectively enhance mmWave OFDM communication links in practical scenarios.