Dynamic Modelling of Liquid Crystal-Based Metasurfaces and its Application to Reducing Reconfigurability Times

TL;DR

This paper introduces a dynamic modelling approach for liquid crystal-based metasurfaces that significantly reduces reconfigurability times, validated through experiments at mm- and sub-mm wave frequencies, enabling faster antenna reconfiguration.

Contribution

It presents the first dynamic model of LC-based cells and a bias signal design tool that drastically improves reconfiguration speed in high-frequency antennas.

Findings

Validated the dynamic LC model experimentally.

Achieved orders of magnitude reduction in reconfiguration times.

Simplified the model without losing accuracy.

Abstract

This paper describes and validates for the first time the dynamic modelling of Liquid Crystal (LC)-based planar multi-resonant cells, as well as its use as bias signals synthesis tool to improve their reconfigurability time. The dynamic LC director equation is solved in the longitudinal direction through the finite elements method, which provides the z- and time-dependent inhomogeneous permittivity tensor used in an electromagnetic simulator to evaluate the cells behaviour. The proposed model has been experimentally validated using reflective cells for phase control (reflectarray) and measuring the transient phase, both in excitation and relaxation regimes. It is shown how a very reduced number of stratified layers are needed to model the material inhomogeneity, and that even an homogeneous effective tensor can be used in most of the cases, which allows a model simplification suitable for design procedures without losing accuracy. Consequently, a novel bias signal design tool is proposed to significantly reduce the transition times of LC cells, and hence, of electrically large antennas composed of them. These tools, similar to those used in optical displays, are experimentally validated for the first time at mm- and sub-mm wave frequencies in this work, obtaining an improvement of orders of magnitude.