The unit cell dynamics of Liquid-Crystal (LC) based reflectarray antennas and Reconfigurable Intelligent Surfaces have been recently analyzed. However, the temporal evolution of the radiation pattern, which can differ from the individual cell response, has not been thoroughly studied. In this paper, a methodology to analyze the dynamic far-field radiation is proposed and tested for two LC antennas. This can open the door to the relaxation of temporal requirements and to achieve further antenna-level response time optimization.

This paper introduces a low-cost, easy-tomanufacture, dual polarization reconfigurable reflectarray antenna based on Liquid Crystal (LC) that operates at W-band. The antenna is electrically large and is capable of independently steering the beam of two orthogonal polarizations. Two different implementations of single-layer unit cells (single resonant and multi-resonant) capable of providing suitable phase range to independently control the two RF polarizations with enough isolation have been investigated. The single resonant cell was finally used to design, manufacture and test a complete reflectarray antenna made of 55×55 elements, for which an accurate and efficient modeling of the cells was implemented. The effect of the LC bias lines is minimized by following a thorough impact study. At a cell level, the measurements validate both the modeling and the capability of the LC to be locally biased at the same cell provided that the biasing network and the resonators of each polarization are properly distributed. At an antenna level, the  measurements are predicted by simulations with excellent accuracy, which validates the design and modeling process. The measured antenna shows 35º of 1D scanning range with 25dBi gain and a maximum SLL of -9dB in the entire range for both polarizations at 98 GHz

Liquid Crystal-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 towards overcoming the temporal problem by using Dual Frequency Liquid Crystals (DFLC) is presented. This paper 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 50x50 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 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.