Analysis And Research Of Electric Scanning Antenna Based On Metamaterial

Phased array technology can control the beam pointing of antenna array.Compared with traditional mechanical scanning mode,the beam scanning speed of antenna is faster and the precision is higher.With the wide application and development of phased array technology in target search,recognition and tracking,the phased array antenna with wide angle and low side lobe scanning characteristics has become the focus of research in the field of antenna.In order to realize the wide angle and low side lobe scanning characteristics of phased array antenna,artificial electromagnetic materials are applied to the design of antenna structure.The characteristics of antenna elements and arrays loaded with artificial electromagnetic materials are studied and analyzed.Phase shifter is the key component of phased array antenna,its characteristics will affect the performance of the whole phased array.Traditional phase shifter based on ferrite,varactor and switch have many problems,such as large volume,slow response speed,high power consumption,high insertion loss and high cost.However,the physical properties of liquid crystal materials at high frequencies(greater than 10GHz)are stable and the loss is small,and the dielectric constant of liquid crystal can change under the action of bias voltage.The phase shifter based on liquid crystal materials has become a research hotspot in recent years due to its advantages of simple structure design,low loss,continuous phase adjustment and low cost.Based on the above research background,a mushroom-type Epsilon Negative Transmission Line(ENG TL)element is used in the design of antenna elements to reduce mutual coupling,and a high impedance surface element supporting surface wave propagation is used in the antenna structure to expand the beam width of the antenna and realize wide-angle scanning of the phased array antenna beam.In order to realize the scanning characteristics of phased array,liquid crystal material is used in the design of phase shifter.The main research contents of the dissertation are summarized as follows:First,antenna design based on ENG TL structure.The ENG TL structure used in the design of antenna elements can effectively reduce the mutual coupling in the array environment and the backward radiation of the antenna.However,the size of the antenna element increases with the loading of ENGTL structure,and the spacing of the elements has to be increased in the array environment,resulting in the occurrence of grating lobes in the array.In this paper,the antenna element is miniaturized by reasonable slots in the antenna and ENG TL structure.It is applied to phased array,which enlarges the scanning range of the array.Combined with the array optimization algorithm,the side lobe level in the scanning process of the array is reduced.Finally,by slotting the central radiation patch,two degenerate mode separation elements with 90 degree phase difference are generated,and the circular polarization radiation of the antenna element is realized.Second,antenna design based on high impedance surface.Based on the classical mushroom-type structure,a rectangular mushroom-type element is designed,and the structure element is miniaturized by slitting.The influence of the structural parameters of the element on the band gap characteristics is analyzed.In addition to the band gap,according to the characteristics of the structure supporting surface wave propagation,a wide-beam antenna element is designed and an array is formed.By controlling the feed phase of each element,the wide-angle scanning of the array is realized.Thirdly,phase shifter design based on liquid crystal materials.Based on the dielectric anisotropy of liquid crystal material and the traditional microstrip line phase shifter structure,a microstrip line phase shifter with adjustable phase shift is designed by using liquid crystal material as the filling medium of microstrip line.Various structural factors affecting the performance of microstrip phase shifter are analyzed.The final design of microstrip phase shifter has the characteristics of large phase shift,low insertion loss and miniaturization.The size of microstrip line phase shifter will increase when a larger phase shift is needed.The size of the phase shifter can be reduced by reasonably designing the structure of the reflection load.Traditional reflective phase shifters loaded with switching elements or varactor reactance networks increase insertion loss when operating frequency increases.The load reactance of liquid crystal material changes with the change of dielectric constant of liquid crystal.When the working frequency increases,the physical characteristics of liquid crystal remain stable and the loss is lower.The performance of phase shifter can be effectively improved by replacing the traditional varactor diode or switching element.