Hardware Implementation of Reflective Intelligent Surfaces for 6G communication networks

The current research on the sixth generation of mobile communication strongly suggests the introduction of new technologies which allow for an advanced control of the radio channel. One motivation for the new paradigm are the increasing operation frequencies which are reaching the subTHz regime. With that trend, the path loss increases as well. One approach to overcome the limitation is the introduction of reflective intelligent surfaces and with that the transition to a flexible control of the radio channel. This paper provides an overview of the building blocks which are required to implement RIS hardware. Open questions, trade-offs and challenges are discussed. Special attention is given to the requirements of the used unit elements and the consequences for the overall RIS design. For the application in the subTHz regime, a LC-based RIS unit element with high efficiency and a maximum phase shift of more than 300 deg is introduced and compared to a reference design for a static reflector. Both designs are optimized for 150 GHz.The static reflector was manufactured and experimentally vali- dated.