| Rencently,liquid crystal has been increasingly applied to the design of microwave devices because of their continuous tunability of dielectric constant and low loss in high frequency bands.However,liquid crystal materials are anisotropic and heterogeneous distributed in microwave devices.This complexity leads to the difficulties in accurate modeling and numerical simulation of liquid crystal microwave devices,resulting in lack of corresponding technical support for the design work.Considering the above problems,the vector method based on the finite difference numerical solution method is used to accurately simulate the liquid crystal molecular director taking the dielectric property of liquid crystal materials and energy coupling relationship as the entry point.And then the liquid crystal microwave electric tuning characteristics and noise were further studied.In addition,the design method of the liquid crystal polarization antenna was deeply discussed.In this paper,the research work is significant for the development of adjustable microwave device technologies such as liquid crystal microwave phase shifters and beam scanning antennas.The research content of this article focuses on the following aspects.Firstly,the dielectric properties of liquid crystal materials and the elastic deformation theory of continuum are studied in this paper.The Friedel Transition phenomenon of liquid crystal molecules under the control of electric field is discussed.And the theoretical derivation of the liquid crystal director calculations has been completed.The mathematical expression of the coupling mechanism between the elastic energy of liquid crystals and the electric field energy is obtained,which provides a theoretical basis for further research.Secondly,based on the dielectric response characteristics of liquid crystals and the energy coupling theory,a method for modeling the internal electric field of inhomogeneous anisotropic media and a method for calculating the director of liquid crystal based on the vector method are respectively completed.Then,the dynamic crossiteration method based on the finite difference method was used to calculate the liquid crystal molecular field and electric field,and the distributions of the liquid crystal director,the permittivity tensor and the electric field in microstrip lines under different control voltages were obtained.The liquid crystal region is semi-automatically modeled using the VBA language in the CST software to verify the potential field of the liquid crystal region in MATLAB,and the effectiveness of the solution method is proved.Then,based on this method,the noise is coupled into the total energy of the liquid crystal system,and the tuning device of the microstrip line is simulated.The influence of noise on the microwave characteristics such as characteristic impedance and phase shift constant is studied.Finally,based on the solution method,a phase shifter with a continuously adjustable phase shift from 0° to 180° is designed and its tuning rate is studied.Furthermore,a polarization antenna based on the phase shifter is designed.The antenna can realize continuous adjustment between the four polarization states of ?45? linear polarization,left-hand and right-hand circular polarization. |
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