A Wideband Reconfigurable Surface Enabled by Schiffman Phase Shifter for 6G cmWave OAM Beam Scanning

This paper introduces a compact wideband Reconfigurable Intelligent Surface (RIS) leveraging Schiffman phase shifters to overcome the traditional narrowband limitations of RIS technology. The proposed design achieves ±15∘ phase balance across a broad frequency range of 7.5–13 GHz, addressing a key challenge in RIS design. The proposed RIS features a compact unit cell, with dimensions of (0.25λ×0.25λ) at 10.25 GHz, integrating a single PIN diode and a tailored internal geometry to enable efficient phase control and scalable implementation. Experimental validation is carried out in two phases: initially, the unit cell is characterized using a waveguide setup; subsequently, a 30cm×30cm RIS panel is fabricated and tested under horn antenna excitation. The measured data exhibit strong agreement with simulations, demonstrating the accuracy and robustness of the proposed design. The full RIS surface is further evaluated for its reconfigurability and ability to generate Orbital Angular Momentum (OAM) beam scanning. These findings highlight the design’s potential for enabling key 6G communication features, offering a compact and wideband RIS solution through the integration of Schiffman phase shifters and contributing to advancements in next-generation wireless systems.