This work studies the wideband modeling and beamforming design of beyond diagonal reconfigurable intelligent surface (BD-RIS), which generalizes and goes beyond conventional RIS with diagonal phase shift matrices to achieve enhanced channel gain. Specifically, we investigate the response of BD-RIS in wideband systems by going back to its hardware circuit realizations. We propose a novel wideband model which has simple expressions while capturing the response variations of BD-RIS for signals with different frequencies. With this wideband model, we propose a BD-RIS design algorithm for an orthogonal frequency division multiplexing system to maximize the average rate over all subcarriers. Finally, we provide simulation results to evaluate the performance of the proposed design and show the importance of wideband modeling for BD-RIS.

翻译：本文研究了超对角可重构智能表面（BD-RIS）的宽带建模与波束赋形设计，该技术通过超越传统采用对角移相矩阵的RIS，实现了信道增益的增强。具体而言，我们通过回溯BD-RIS的硬件电路实现，探究其在宽带系统中的响应特性。我们提出了一种新型宽带模型，该模型在具备简洁表达式的条件下，能够捕捉BD-RIS对不同频率信号响应变化。基于此宽带模型，我们针对正交频分复用系统提出了一种BD-RIS设计算法，以最大化所有子载波上的平均速率。最后，我们通过仿真结果评估了所提设计的性能，并论证了宽带建模对BD-RIS的重要性。