Reconfigurable intelligent surfaces have emerged as a promising hardware platform for shaping wireless propagation environments at millimeter-wave (mm-Wave) frequencies and beyond. While many existing studies emphasize channel modeling and signal processing, practical RIS deployment is fundamentally governed by hardware design choices and their system-level implications. This paper presents a hardware-centric overview of recent mm-Wave RIS developments, covering wideband realizations, high-resolution phase-quantized designs, fully printed low-cost implementations, optically transparent surfaces, RIS-on-chip solutions, and emerging three-dimensional architectures. Key challenges including mutual coupling, calibration, multi-RIS interaction, and frequency-dependent phase control are discussed to bridge hardware realization with system-level optimization. This overview provides practical design insights and aims to guide future RIS research toward scalable, efficient, and practically deployable intelligent surface architectures.
@article{arxiv.2602.23345,
title = {Millimeter-Wave RIS: Hardware Design and System-Level Considerations},
author = {Ruiqi Wang and Pinjun Zheng and Yiming Yang and Xiarui Su and Mohammad Vaseem and Anas Chaaban and Md. Jahangir Hossain and Tareq Y. Al-Naffouri and Atif Shamim},
journal= {arXiv preprint arXiv:2602.23345},
year = {2026}
}