Design and SDR Validation of a 5.8 GHz 1-bit Reconfigurable Intelligent Surface With Optimized RF Choke

Reconfigurable Intelligent Surfaces (RIS) have recently attracted significant attention as a means to control the propagation environment, enabling improved signal coverage, interference management, and more efficient spectrum utilization. This work presents a 1-bit RIS operating at 5.8 GHz, designed for wide-angle beam steering and real-time software-defined radio (SDR) validation. While many earlier 1-bit RIS designs demonstrated steering angles up to about 45°, the proposed design extends the range to 60°, with a realized gain of 22.60 dBi at 10° and 14.62 dBi at 60°. The unit cell, fabricated on a RO4350B substrate, features a tailored RF choke structure that suppresses mutual coupling and limits RF leakage, thereby improving phase stability, a key aspect rarely emphasized in prior RIS studies. Experimental validation using an SDR-based testbed confirms significant signal quality improvements, including a 57.4% reduction in error vector magnitude (EVM), from 57.30% to 24.39%, and a 7.42 dB increase in signal-to-noise ratio (SNR), resulting in better QPSK video transmission. Additionally, orbital angular momentum (OAM) beamforming capabilities were explored via full-wave simulations, demonstrating feasible generation of modes 1, 2, and 3 for potential multiplexing. This RIS offers a scalable, energy-conscious, and cost-effective solution by integrating low-cost PIN diodes (SMP1320-079LF) and an efficient biasing network. The presented RIS architecture aligns with emerging 5G/6G network requirements and can support applications including adaptive indoor coverage, UAV-assisted links, and holographic MIMO.