Thanks to the application of metamaterials, holographic multiple-input multiple-output (H-MIMO) is expected to achieve a higher spatial diversity gain with lower hardware complexity. With the aid of a circular antenna arrangement of H-MIMO, integrated data and energy multicast (IDEM) can fully exploit the near-field channel to realize wider range of energy focusing and higher achievable rate. In this paper, we derive the closed-form near-field resolution function in 3D space and show the asymptotic spatial orthogonality of near-field channel for circular antenna array. We then investigate the beamforming designs for IDEM systems, where the minimum rate of data users (DUs) are maximized while guaranteeing the energy harvesting requirements for energy users (EUs). Specifically, the asymptotically optimal fully-digital beamformer is first obtained based on the spatial orthogonality. Then, the alternating optimization is adopted for the H-MIMO beamforming, where the digital beamformer is obtained in closed form and the analog beamformers of three different control modes are then obtained, respectively. Scaling schemes are also investigated to further improve the IDEM performance. Numerical results verify the correctness of the resolution function and asymptotic orthogonality. Moreover, the proposed beamforming schemes with very low complexity outperform benchmark schemes.

翻译：得益于超材料的应用，全息多输入多输出（H-MIMO）有望以较低的硬件复杂度实现更高的空间分集增益。借助H-MIMO的圆形天线排布，集成数据与能量多播（IDEM）系统能够充分利用近场信道，实现更广的能量聚焦范围和更高的可达速率。本文推导了三维空间中近场分辨率函数的闭式表达式，并证明了圆形天线阵列近场信道的渐近空间正交性。随后，我们研究了IDEM系统的波束成形设计，其目标是在保障能量用户（EUs）能量收集需求的前提下，最大化数据用户（DUs）的最小速率。具体而言，首先基于空间正交性获得了渐近最优的全数字波束成形器；接着采用交替优化方法求解H-MIMO波束成形问题，其中数字波束成形器以闭式形式获得，而三种不同控制模式的模拟波束成形器则分别求解。此外，还研究了缩放方案以进一步提升IDEM系统性能。数值结果验证了分辨率函数与渐近正交性的正确性。所提出的波束成形方案复杂度极低，且性能优于基准方案。