Towards Terahertz Liquid Crystal Reconfigurable Intelligent Surface based on Defected Delay Lines

This paper presents the design of a liquid crystal (LC) reconfigurable intelligent surface (RIS) operating around 240GHz. The architecture is based on a delay line phase shifter with a defected ground structure coupled to a patch antenna. The phase shifter features a LC layer thickness of 4.6µm, a figure of merit of 54°/dB and a compactness of 371°/λ<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</inf> at 240GHz. The designed RIS operates between 222GHz and 250GHz, and, hence, exhibits a bandwidth of more than 10% and a maximum aperture efficiency of 12.3% all while utilizing lossy materials and a minimum feature size of 20µm.