Three-dimensional accurate modeling of nematic liquid crystal based dipole unit for reconfigurable reflectarray at 100 GHz

Abstract

Abstract In this paper, a three-dimensional accurate modeling of nematic liquid crystal (LC) has been presented for the analysis of reconfigurable reflectarray cells based on LC. Both single-dipole and multiple-dipoles constructed on a LC substrate are designed as the reflectarray unit cell. Considering the inhomogeneous and anisotropic effects, the orientation of the LC molecules at each point of the LC layer involved in the unit cell under the external electrostatic field is obtained by the finite difference numerical modeling method. Utilizing the accurate modeling results of LC, the reflection constants of the reflectarray unit cells have been simulated and also have been compared with that of in the conventional model which usually assumes the LC is homogeneous and isotropic (HOMI). The error of phase range of the unit cell between the two models can exceed 45° in the single-resonant unit cell, and is more than 290° in the multi-resonant unit cell, which will seriously affect the practical application. The permittivity of LC in the unit cells under different applied voltages also has been calculated and given. Moreover, the gain radiation pattern of the reflectarray consisting of the proposed LC based double-dipoles unit cell is simulated in two models. The simulation results show that, in the accurate modeling, the gain and scanning angle range of the reflectarray obtained by the HOMI model change significantly because the phase-shift of the same unit cell for the incident wave is greatly different in the two models, which indicates that the HOMI model can no longer meet the needs of the design of LC based multi-dipoles reflectarray. Therefore, the accurate modeling method needs to be considered and cannot be ignored when studying and designing LC based devices.