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：本文研究了在可重构智能表面（RIS）元件之间存在互耦的情况下，超越对角可重构智能表面辅助无线通信系统的建模与优化问题。具体而言，我们首先利用散射参数和阻抗参数分析，推导出考虑互耦的BD-RIS辅助通信模型。基于所获得的通信模型，我们提出了一种通用的BD-RIS优化算法，该算法可适用于不同架构的BD-RIS，以最大化信道增益。数值结果验证了所提设计的有效性，并表明互耦越强，BD-RIS相较于传统对角RIS提供的增益越大。