Research On Large Angle Beam Scanning Reflective Array Antenna Based On Liquid Crystal

Modern communication scenarios are becoming more and more complex,and the demand for multifunctional,miniaturized and low-cost communication systems is becoming stronger and stronger.Therefore,the antenna with strong directivity and continuous beam scanning function is of great value to the function,structure and cost of the whole communication system.Planar reflective array has been widely used in beam scanning antenna because of its relatively simple structure and accurate beam pointing.At present,there are three main ways to realize antenna beam scanning: mechanical tuning drive,electronic device tuning and electronic control material tuning.As a common electronic control material,liquid crystal has the characteristics of adjustable dielectric constant and low dielectric loss in high frequency band.Therefore,the beam scanning antenna based on liquid crystal material can realize electronically controlled continuous beam scanning,and can work in high frequency band.In this paper,two kinds of liquid crystal planar reflective array antennas working in different frequency bands are studied.The main work is as follows:1.The electromagnetic properties of liquid crystal materials are studied.The molecular characteristics of liquid crystal materials and the principle of dielectric anisotropy are analyzed,and a wafer resonator for measuring the dielectric constant of liquid crystal is designed.Based on the resonance method,the variation range of the dielectric constant of liquid crystal under different applied voltages in millimeter wave band is obtained.2.The electronically controlled beam scanning reflective array antenna based on liquid crystal material in Ka band is studied.Firstly,aiming at the problems of insufficient phase shift and poor linearity of phase shift curve of traditional liquid crystal reflection unit,a ring dipole liquid crystal reflection unit is designed in this paper.The maximum405 ° phase shift can be obtained at the frequency of 35 GHz,and the reflection loss is less than 4.5db.Then,based on the unit,a liquid crystal planar reflection array antenna in Ka band is designed,and the array contains 11 × 11 reflection units with a diameter of55 mm × 55 mm,realizing continuous beam scanning of ± 45 ° in one-dimensional direction.Finally,the antenna is processed and tested.The measured results show that the array antenna can realize ± 20 ° electronically controlled continuous beam scanning in one-dimensional direction.3.Terahertz planar reflective array antenna based on liquid crystal material is studied.In this study,quartz glass is used as the upper and lower dielectric substrates of liquid crystal reflection array antenna,and a double dipole liquid crystal reflection unit is designed.The reflection unit can obtain a maximum 365 ° phase shift at 107.5ghz frequency,and the reflection loss is less than-3.5db,and a 19×19 liquid crystal planar reflection array antenna working in the terahertz band is designed by using this unit.The simulation results show that the liquid crystal planar reflective array antenna realizes ±30 ° continuous beam scanning in one-dimensional direction.The maximum gain of the antenna is 16.9dbi and the maximum sidelobe level is-6d B.