Research On Key Technologies Of Miniaturized Liquid Crystal Phase Shifter With Large Phase Shift

As a device for controlling the phase of signals,phase shifters are widely used in phased array systems,microwave phase measurement,digital mobile communications,adaptive antennas and phase modulation systems.With the fast growing development of modern communication,it is of great significance to study the dynamic and continuously adjustable microwave phase shifter.As a dielectric tunable material,liquid crystal has the characteristics of continuous tuning,low cost and easy integration.This thesis mainly carries out the research on the key technology of liquid crystal phase shifter with miniaturization and large phase shift.The specific work is as follows:1.Two liquid crystal phase shifters working in Ku-band are developed.Firstly,a liquid crystal phase shifter with microstrip line is designed,and the miniaturization of the phase shifter is achieved by the use of bent lines and chamfered corners.The designed phase shifter achieves a maximum differential phase shift of 363° in the14-16 GHz frequency band,the insertion loss is better than 3.3d B,and the return loss is less than-22 d B.Experiments show that the bent microstrip liquid crystal phase shifter achieves a maximum differential phase shift of 102° during the voltage tuning process of 0-20 V.In order to further improve the miniaturization of the liquid crystal phase shifter,a multi-layer structure reflective liquid crystal phase shifter based on a 3d B coupler is proposed.Change the load impedance of the 3d B coupler port by adjusting the dielectric constant of the liquid crystal,so as to realize the phase change of the coupler output.In the working frequency band of 14GHz-16 GHz,the return loss is better than-10.2d B,the insertion loss is better than 5.8d B,and the maximum differential phase shift reaches 366°.Experiments show that the reflective liquid crystal phase shifter achieves a maximum differential phase shift of 128° during voltage tuning from 0 to 20 V.2.A liquid crystal phase shifter working in the Q-band is designed.The coplanar waveguide structure based on artificial surface plasmon is studied.The transmission line adopts periodic metal strip structure to increase the phase shift amount per unit length,thereby realizing the miniaturization of the phase shifter.The designed phase shifter has a return loss of less than-15 d B in the 42GHz-48 GHz operating frequency band,an insertion loss of better than 5.1d B,and a maximum differential phase shift of 389°.3.A liquid crystal phase shifter working in the terahertz frequency band is designed.Firstly,a terahertz liquid crystal phase shifter based on dielectric waveguide is designed,the working frequency band is 100GHz-110 GHz,the return loss of the phase shifter in the process of liquid crystal tuning is less than-17.8d B,the maximum insertion loss is 4.9d B,and the maximum differential phase in the frequency band is363°.The liquid crystal phase shifter is then applied to a 1×4 terahertz array antenna.The simulation results show that by changing the liquid crystal dielectric constant of each phase shifter in the antenna,the terahertz array antenna can achieve ±8.5° beam scanning at 105 GHz.