THz Electronically Steerable Transmitarray Antenna Based On Liquid Crystal

THz electronically steerable antenna can control beam direction flexibly,which enhance the timeliness and accuracy of THz application system.Thus it becomes a hot topic of terahertz antenna technology research.At present,beam scanning is usually achieved using graphene and liquid crystal as tunable dielectric in THz electronically steerable antenna.however,limited by the preparation technology,high purity of graphene with big area is difficult to product on a large scale for now,which limits the promotion of graphene in the terahertz antenna technology.In the electronically scanned reflectarray antenna based on liquid crystal,the block of the feed horn has a big influnces on the scanning range of the main lobe.In order to solve those problems,this thesis utilizes the liquid crystal to design the transmitarray antenna with beam scanning ability.First,a single-layer liquid crystal phase shifter is designed,and the phase range from zero to maximum bias voltage is 90° at 340 GHz.Secondly,in order to increase the phase shift of the array cells,a double-layer liquid crystal phase shifter which has a phase shift of 180° at 340 GHz is designed,and the insertion loss of the unit is always maintained at about 1 d B.Finally,the liquid crystal electronically steerable transmiarray antenna with 1-bit phase resolution is designed based on the double layer liquid crystal phase shifter,and the beam scanning range reaches-40° ~ +40°.The electronically steerable transmiarray antenna based on liquid crystal provides a new method for the design of electronically steerable terahertz antenna.The dielectric properties of liquid crystal are aslo studied in this paper.From the point of the direction of the RF field and the electrostatic field in the liquid crystal material,a new method of optimizing the tuning range of liquid crystal equivalent dielectric constant is proposed.By modeling the angle difference between the direction of the RF field and the electrostatic field and use the decentralized ideas to reconcile the relationship between the angle difference and the RF field of any position in the liquid crystal layer,then the tuning range of liquid crystal equivalent dielectric constant is judged.And the correctness of this optimization method is verified by simulation.This kind of optimization method has certain reference value for the design of liquid crystal tuner in the future.