Traditional point-to-point line-of-sight channels have rank 1, irrespective of the number of antennas and array geometries, due to far-field propagation conditions. By contrast, recent papers in the holographic multiple-input multiple-output (MIMO) literature characterize the maximum channel rank that can be achieved between two continuous array apertures, which is much larger than 1 under near-field propagation conditions. In this paper, we maximize the channel capacity between two dual-polarized uniform rectangular arrays (URAs) with discrete antenna elements for a given propagation distance. In particular, we derive the antenna spacings that lead to an ideal MIMO channel where all singular values are as similar as possible. We utilize this analytic result to find the two array geometries that respectively minimize the aperture area and the aperture length.

翻译：传统点对点视距信道因远场传播条件，无论天线数量与阵列几何结构如何，其秩均为1。相比之下，全息多输入多输出领域的近期研究揭示了两个连续孔径阵列间可实现的最大信道秩，该值在近场传播条件下远大于1。本文针对给定传播距离，优化了具有离散天线单元的双极化均匀矩形阵列间的信道容量。具体而言，我们推导了能使所有奇异值尽可能相似的最优天线间距，从而构建理想MIMO信道。基于该解析结果，我们分别确定了使孔径面积和孔径长度最小化的两种阵列几何结构。