The ability of reconfigurable intelligent surfaces (RIS) to produce complex radiation patterns in the far-field is determined by various factors, such as the unit-cell's size, shape, spatial arrangement, tuning mechanism, the communication and control circuitry's complexity, and the illuminating source's type (point/planewave). Research on RIS has been mainly focused on two areas: first, the optimization and design of unit-cells to achieve desired electromagnetic responses within a specific frequency band; and second, exploring the applications of RIS in various settings, including system-level performance analysis. The former does not assume any specific radiation pattern on the surface level, while the latter does not consider any particular unit-cell design. Both approaches largely ignore the complexity and power requirements of the RIS control circuitry. As we progress towards the fabrication and use of RIS in real-world settings, it is becoming increasingly necessary to consider the interplay between the unit-cell design, the required surface-level radiation patterns, the control circuit's complexity, and the power requirements concurrently. In this paper, a benchmarking framework for RIS is employed to compare performance and analyze tradeoffs between the unit-cell's specified radiation patterns and the control circuit's complexity for far-field beamforming, considering different diode-based unit-cell designs for a given surface size. This work lays the foundation for optimizing the design of the unit-cells and surface-level radiation patterns, facilitating the optimization of RIS-assisted wireless communication systems.

翻译：可重构智能表面（RIS）在远场中产生复杂辐射模式的能力取决于多种因素，例如单元尺寸、形状、空间排列、调谐机制、通信与控制电路的复杂度，以及照明源的类型（点源/平面波）。RIS的研究主要集中于两个领域：一是优化和设计单元以在特定频段内实现所需的电磁响应；二是探索RIS在各种场景中的应用，包括系统级性能分析。前者未假设表面级存在任何特定的辐射模式，而后者则未考虑任何特定的单元设计。这两种方法在很大程度上忽略了RIS控制电路的复杂性和功耗需求。随着我们逐步向实际环境中制造和应用RIS迈进，越来越需要同时考虑单元设计、所需的表面级辐射模式、控制电路复杂度以及功耗需求之间的相互作用。本文采用一种RIS基准框架，基于给定表面尺寸下不同二极管型单元设计，比较远场波束成形的性能并分析单元指定辐射模式与控制电路复杂度之间的权衡。这项工作为优化单元和表面级辐射模式的设计奠定了基础，有助于优化RIS辅助的无线通信系统。