Low-Loss Reflective Intelligent Surface Based on Polarization-Rotation for 6G FR3 Band Applications

Addressing the need for efficient channel control in 6G networks, we introduce a novel 3-bit reflective intelligent surface (RIS) concept. It is compatible with low-cost FR4 printed circuit board technology and operates at the 7.125-8.4 GHz FR3 band. The core innovation proposed here is the use of internal reflections between a polarization rotator and a filter, which successfully enhances the phase shift up to 307°. The method allows an efficient unit cell design maintaining a high reflection coefficient above -0.9 dB. The final RIS panel demonstrates reliable beam steering up to 50°. It shows a minimal performance degradation, with a maximum amplitude difference below -1.1 dB relative to the theoretical scan loss.