标题： 基于液晶技术的可重构智能表面：硬件设计与通信视角 显示英文标题

标题： Reconfigurable Intelligent Surfaces with Liquid Crystal Technology: A Hardware Design and Communication Perspective

摘要： 随着关于可重构智能表面（RISs）在无线通信和感知方面的理论工作的激增，迫切需要硬件解决方案来评估这些理论结果并进一步推动该领域的发展。文献中提出的最常见的解决方案是基于变容二极管、正本征负（PIN）二极管和微机电系统（MEMS）。本文介绍了液晶（LC）技术在实现连续可调的超大规模毫米波RISs中的应用。我们回顾了液晶理论的基本物理原理，介绍了两种不同的液晶-RISs实现方式，即反射阵列和相位阵列，并强调了它们对系统设计和RIS重新配置策略有影响的关键特性。此外，从可行性、成本、功耗、重新配置速度和带宽等方面将液晶技术与竞争技术进行了比较。此外，还提出了液晶-RISs在理论和实验研究中的几个重要开放问题。 显示英文摘要

摘要： With the surge of theoretical work investigating Reconfigurable Intelligent Surfaces (RISs) for wireless communication and sensing, there exists an urgent need of hardware solutions for the evaluation of these theoretical results and further advancing the field. The most common solutions proposed in the literature are based on varactors, Positive Intrinsic-Negative (PIN) diodes, and Micro-Electro-Mechanical Systems (MEMS). This paper presents the use of Liquid Crystal (LC) technology for the realization of continuously tunable extremely large millimeter-wave RISs. We review the basic physical principles of LC theory, introduce two different realizations of LC-RISs, namely reflect-array and phased-array, and highlight their key properties that have an impact on the system design and RIS reconfiguration strategy. Moreover, the LC technology is compared with the competing technologies in terms of feasibility, cost, power consumption, reconfiguration speed, and bandwidth. Furthermore, several important open problems for both theoretical and experimental research on LC-RISs are presented.