Beyond Diagonal Reconfigurable Intelligent Surfaces with Mutual Coupling: Modeling and Optimization

TL;DR

This paper models and optimizes beyond diagonal reconfigurable intelligent surfaces (BD-RIS) considering mutual coupling, showing that mutual coupling can enhance channel gain compared to conventional RIS.

Contribution

It introduces a mutual coupling aware modeling framework for BD-RIS and proposes a general optimization algorithm applicable to various architectures.

Findings

Mutual coupling increases the channel gain in BD-RIS systems.

The proposed optimization algorithm effectively maximizes channel gain.

Numerical results confirm the benefits of considering mutual coupling in BD-RIS design.

Abstract

This work studies the modeling and optimization of beyond diagonal reconfigurable intelligent surface (BD-RIS) aided wireless communication systems in the presence of mutual coupling among the RIS elements. Specifically, we first derive the mutual coupling aware BD-RIS aided communication model using scattering and impedance parameter analysis. Based on the obtained communication model, we propose a general BD-RIS optimization algorithm applicable to different architectures of BD-RIS to maximize the channel gain. Numerical results validate the effectiveness of the proposed design and demonstrate that the larger the mutual coupling the larger the gain offered by BD-RIS over conventional diagonal RIS.