Mutual Coupling in RIS-Aided Communication: Experimental Validation and Performance Evaluation

This paper explores the mutual coupling in the reconfigurable intelligent surface (RIS)-aided communication. Despite the existence of several mutual coupling-aware models for RIS-aided communication, a notable gap remains due to the lack of experimental validation. This paper bridges this gap by first introducing a novel model training approach based on the 3D full-wave simulation and subsequently validating the obtained model via experimental measurements in a 1-bit quasi-passive RIS prototype operating in the mmWave band. Comparative analyses reveal precision in both the employed mutual coupling-aware model and the assessed model parameters, offering a realistic evaluation of mutual coupling in authentic RIS hardware. Utilizing the validated mutual coupling-aware communication model, we systematically examine the impact of mutual coupling on communication performance by adopting the achievable rate as a performance indicator. Our results reveal that the mutual coupling in RIS exhibits heightened significance with increased RIS amplitude gains and showcases a frequency-dependent effect.