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：本研究探讨了在可重构智能超表面（RIS）单元间存在互耦效应的情况下，超越对角可重构智能超表面（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与阻抗参数分析，推导了考虑互耦效应的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架构的通用优化算法，以最大化信道增益。数值仿真结果验证了所提设计的有效性，并表明互耦效应越强，BD-RIS相比传统对角RIS所能提供的性能增益越大。