Liquid Crystal-Based RIS Loss-Trade-Off Analysis

Liquid crystal (LC) technology has emerged as a promising solution for large reconfigurable intelligent surfaces (RISs) at millimeter wave (mmWave) bands, offering advantages such as low power consumption, scalability, and continuously tunable phase shifts. For LC-RIS based on the delay-line architecture, i.e., with dedicated phase shifters, there exists a tradeoff between the maximum achievable phase-shift range and the corresponding insertion loss, which has not been studied for LC-RIS-assisted wireless systems yet. In this paper, we investigate this trade-off where a base station (BS) and an RIS are configured to minimize the transmitter (Tx) power while satisfying a given quality of service (QoS) for a number of users. Simulation results reveal a fundamental trade-off between the total Tx power and the achievable data rate as a function of the LC phase-shift range.