Design And Application Of Polarization Conversion Metasurface

As a kind of new material different from natural materials,metamaterials have a lot of properties not found in natural materials and have been widely used in antenna design in recent years.The polarization conversion metasurface is a special kind of metamaterial,which can change the polarization of the electromagnetic wave,and has great application value in the electromagnetic field.Recently the polarization conversion metasuface has been studied by more and more scholars and a variety of high-performance polarization conversion metasurfaces have been proposed in literature,whose characteristics have been utilized to provide the antenna more excelent functions,especially in field of its ability to generate circularly-polarized radiation and low scattering characteristic of antennas.Based on the design of linear polarization to cross-polarization and linear polarization to circular polarization conversion metasurface,this thesis focuses on the research and design of low RCS and circularly polarized antenna.The first part of this thesis expounds the researching background of metamaterials as well as the application of polarization conversion metasurface in the realization of circularly polarized radiation and low RCS of antennas.Subsequently,the current research status of two common polarization conversion metasurfaces was introduced through recent publications.On the application of polarization conversion metasurface on design of the low scattering antenna,the third part of the thesis presents two kinds of reflective linear polarization to cross-polarization conversion units operating in the high and low frequency bands respectively.Through reasonably controling the numbers and arrangement of the two polarization conversion metasurfaces unit by periodic arrangement and checkerboard layout to realize the ultra-wide bandwidth of the polarization conversion,further forming the ultrawideband low RCS characteristics.On the basis of above design,in order to study its application on the design of low scattering antenna,the polarization conversion metasurface is loaded on the slot array antenna,then a low ultra-wideband low RCS antenna is proposed.The simulation and measurement of the antenna are in good agreement.This design effectively provides a method to expand the RCS reduction bandwidth,which offers a good idea for the design of ultra-wideband low RCS antennas.On the application of polarization conversion metasurface on circularly polarized antenna,the fourth part of the thesis proposes a transmissive polarization conversion unit that can realize the conversion the polarization of electromagnetic waves from linear polarization into circular polarization.And its array is loaded above the rectangular microstrip antenna to form a circularly polarized antenna,and the antenna has good left-handed circular polarization characteristics.Meanwhile,two kinds of artificial magnetic conductor surfaces are further arranged around the microstrip antenna,and the two artificial magnetic conductor surface units and the upper line-to-circular polarization conversion surface respectively constitute two oppositely directed linear-polarized to cross-polarized polarization conversion surface,whose phase difference of retroreflected waves is satisfied with 180°,thereby realizing low RCS characteristic.The antenna can maintain a good gain and lefthanded circular polarization while achieving low RCS characteristics in the operating band.Finally,the circularly polarized low RCS antenna is simulated.The results show that the antenna can achieve low RCS effect while maintaining good radiation characteristics.