Characterization and Application of Dual-Frequency Liquid-Crystal Mixtures in mm-Wave Reflectarray Cells to Improve Their Temporal Response

Liquid-crystal (LC)-based mm-wave spatially fed antennas with electronic reconfiguration are a promising solution at the higher frequencies required in next-generation networks. However, one of the main drawbacks of the technology in these bands stems from the high reconfigurability times they present. Through this work, a relevant step toward overcoming the temporal problem by using dual-frequency LCs (DFLCs) is presented. This article details, for the first time, both the electromagnetic and temporal characterization of four commercially available DFLC mixtures in W-band, enabling their use in designing faster devices. To evaluate the experimental characterization, a reflectarray surface (made of 50 × 50 cells) specifically designed to achieve fast switching times with a sufficient phase range has been manufactured and measured. For this cell, a preliminary addressing technique based on overdriving has been used, exhibiting reconfigurability (rise and decay) times of 20 ms, one order of magnitude faster than the current state of the art of LC-based mm-wave planar devices. The measured results match the simulations and reveal that a precisely designed biasing technique using overdrive (OD) must be used for DFLC-cells to achieve time reduction. Additionally, the benefits of this technology compared with other LC acceleration strategies in mm-wave are discussed.