Hardware Aspects of Sub-THz Antennas and Reconfigurable Intelligent Surfaces for 6G Communications
The need for unrestricted, high-quality, and high-speed communications in planned sixth generation (6G) wireless systems drives the development and research towards the sub-terahertz (sub-THz) bands which so far have been relatively unused for wireless communications applications. Additionally, the sub-THz bands have gained an increasing interest as a potential spectral region at which to go even beyond the well-known Shannon limits. This review paper provides a technological overview on some of the key hardware aspects of sub-THz wireless communications (at 100–300GHz), namely antennas, reconfigurable intelligent surfaces (RISs), and reconfigurable antenna systems based on state-of-the-art technologies reported in recent literature. Different technologies of antennas and RISs are compared to understand their possibilities and limitations, and to identify the most promising technological approaches to transform 6G from a vision into a commercially viable solution. The paper also presents the authors’ interpretations of possible hardware and design trends that can shape the future research directions.