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.

翻译：本文研究了在RIS单元间存在互耦效应的超越对角可重构智能表面（BD-RIS）辅助无线通信系统的建模与优化问题。具体而言，我们首先通过散射参数和阻抗参数分析，推导出考虑互耦效应的BD-RIS辅助通信模型。基于所获得的通信模型，我们提出了一种适用于不同BD-RIS架构的通用BD-RIS优化算法，用于最大化信道增益。数值结果验证了所提方案的有效性，并表明互耦效应越大，BD-RIS相比传统对角RIS所能带来的增益也越大。