Liquid-Crystal-Based Reconfigurable Intelligent Surface for Sub-Terahertz Wireless Communications

Reconfigurable intelligent surfaces (RIS) have received significant attention in the field of communication and wireless networks, due to their numerous advantages, such as low cost, low energy consumption, miniaturization, programmability, and ease of deployment. This paper proposes an RIS based on liquid crystal (LC) for constructing wireless communication systems. Tunable LC embedded between metal microstructures supported by quartz substrates allows for precise control of the reflected wave phase. The experimental results demonstrate that RIS has more than 3600 of phase modulation capability and four stable digital coding states at the optimal operating frequency of 100.2 GHz. In addition, the RIS has a 100∘ beam scanning capability, providing a solid foundation for tracking and targeting during communications. The communication capability of RIS was then demonstrated in the sub-terahertz band by constructing a 16QAM constellation diagram test system and a video real-time transmission system with varying deflection angles. Our work provides excellent solutions for communication and wireless network applications in the millimeter wave and terahertz (THz) frequency bands.