Reconfigurable intelligent surface (RIS) is a new technique that is able to manipulate the wireless environment smartly and has been exploited for assisting the wireless communications, especially at high frequency band. However, it suffers from hardware impairments (HWIs) in practical designs, which inevitably degrades its performance and thus limits its full potential. To address this practical issue, we first propose a new RIS reflection model involving phase-shift errors, which is then verified by the measurement results from field trials. With this beamforming model, various phase-shift errors caused by different HWIs can be analyzed. The phase-shift errors are classified into three categories: (1) globally independent and identically distributed errors, (2) grouped independent and identically distributed errors and (3) grouped fixed errors. The impact of typical HWIs, including frequency mismatch, PIN diode failures and panel deformation, on RIS beamforming ability are studied with the theoretical model and are compared with numerical results. The impact of frequency mismatch are discussed separately for narrow-band and wide-band beamforming. Finally, useful insights and guidelines on the RIS design and its deployment are highlighted for practical wireless systems.

翻译：可重构智能表面（RIS）是一种能够智能调控无线环境的新技术，已被开发用于辅助无线通信，尤其是在高频段。然而，在实际设计中，它受到硬件损伤的影响，这不可避免地降低了其性能，从而限制了其全部潜力。为了解决这一实际问题，我们首先提出了一种包含相移误差的新型RIS反射模型，并通过现场试验的测量结果进行了验证。利用该波束赋形模型，可以分析由不同硬件损伤引起的各种相移误差。相移误差被分为三类：（1）全局独立同分布误差，（2）分组独立同分布误差，以及（3）分组固定误差。采用理论模型研究了典型硬件损伤（包括频率失配、PIN二极管故障和面板变形）对RIS波束赋形能力的影响，并与数值结果进行了对比。对于窄带和宽带波束赋形，分别讨论了频率失配的影响。最后，为实际无线系统提供了关于RIS设计及部署的有用见解和指南。