Research On Circularly Polarized Phased Array Antennas Based On Liquid Crystal Materials

With the development of 5G,6G,satellite Internet and other technologies,the demand for high-performance phased array antennas is also increasing.However,the traditional phased array antenna has the disadvantages of high cost,large volume,unreliability,and discontinuous phase shift,low precision,and high power consumption when controlling Angle scanning,which increasingly can not meet the demand for high-performance devices.Liquid crystal materials have the advantages of low cost and easy conformal integration in microwave devices because of their special physical properties,especially the dielectric anisotropy of liquid crystal.At the same time,liquid crystal materials used in phase shifters have the characteristics of continuous tuning.These advantages make liquid crystal materials become more and more important in the research of microwave devices.In this thesis,the phased array antenna based on liquid crystal materials is studied.The specific work is as follows:1.Propose a C-band linearly polarized phased array antenna based on liquid crystal materials.The antenna adopts the form of 8×8 microstrip antenna,which uses V-like slit and laminate to expand bandwidth and increase gain.Based on the principle of phased array antenna scanning and the tuning principle of liquid crystal materials,an inverted microstrip line liquid crystal phase shifter is used instead of a traditional T/R module phase shifter,which can achieve a 360° phase shift.The integrated structure of antenna,phase shifter and power splitter is realized,and the gain is 20.5dB in C-band,and the beam scanning of ±50° can be realized.2.Propose a C-band circular polarization phased array antenna structure based on liquid crystal materials is proposed.The performance of the traditional inverted microstrip line liquid crystal phase shifter and two reflective liquid crystal phase shifters is designed and compared.The maximum differential phase shifter of the reflective phase shifter is 430° and 461°,respectively,and the results are compared with the traditional inverted microstrip line liquid crystal phase shifter.Based on the research of liquid crystal phase shifter,a 1×4 circular polarized linear array is designed.The simulation results show that the antenna array has the maximum gain of 12.6dB at5.2GHz frequency,and the bandwidth is 5.0GHz～5.4GHz.The measured gain is 9.3dB at the frequency,and the bandwidth is 4.9GHz ～ 5.35 GHz.Can achieve ±25° Angle scanning function.3.Propose a Ka band circular polarization phased array antenna structure based on liquid crystal materials is proposed.In the form of microstrip antenna,circular polarization is realized in the way of perturbation.At the same time,the liquid crystal phase shifter in the form of compact inverted microstrip line is adopted,and the array is arranged in the form of 8×8 at half wavelength.Through software simulation,it can realize the Ka-band,gain is 20 dB,can achieve ±30° beam scanning.