Electromagnetic modeling and simulation of microwave and mm-wave devices based on liquid crystal compounds

Tunable devices and materials have always been extremely important for a variety of applications in the optical as well as the µ-wave and mm-wave bands. With the arrival of 5G communications networks and the ubiquitous use of wireless gadgets and applications ranging from smartphones to the implementation of the Internet of Things (IoT), the need for compact, versatile, and lightweight devices is imperative. Liquid Crystals (LCs) are anisotropic and tunable, and these properties make them an attractive proposition for use in portable devices and communication hubs. In this paper, three such LC-based devices operating in the 5GHz I 30GHz (5G) bands are presented: A frequency-agile patch antenna, a variable phase shifter, and a beam­ steerable leaky wave antenna. In all cases, tunability is achieved via the application of a low-strength external bias electric field. This affects the dielectric properties of the crystal by re-orienting its molecules, the macroscopic orientation of which is denoted by a unit vector called the director. The dielectric properties of the LC-cell are characterized by its relative permittivity tensor, which is a function of the directors' orientation. The latter is determined at every point of the cell by solving a coupled system of partial differential equations (PDEs) numerically. The obtained relative permittivity tensor is input into a high-frequency full­ wave electromagnetic simulator based on the finite-element method (FEM). Finally, the simulation results are analyzed and the performance and capabilities of the applications are discussed.