| The meaning of controlling the polarization state of electromagnetic wave is to adjust and transform the polarization of electromagnetic wave to the anticipated shape by using the physical effects,which are produced by the interaction between electromagnetic wave and material.Polarization control was widely used in the fields of communication,radar and anti-jamming.The ferrite and metal grating were usually used to realize the polarization control in the traditional methods,but the polarization converters designed by them had the disadvantages of large section size,heavy weight and narrow working bandwidth,which were not conducive to system integration.In recent years,the artificial electromagnetic provides a new way to design the high-performance polarization converters because of its advantages of strong polarization conversion ability and light weight.There were two kinds of artificial electromagnetic medium structures that can be used to control the polarization state of electromagnetic wave,including chiral artificial structure and anisotropic artificial structure.Based on these two kinds of artificial structures,the new polarization control technology was studied in this thesis to solve the shortcomings of the polarization converters designed by the traditional method.Then,several different types of polarization conversion units and devices were designed,and their related applications were discussed simultaneously.The main work in this thesis can be summarized as follows:(1)Taking the split-ring resonator(SRR)linearly polarized wave to linearly polarized wave(LP-to-LP)polarization conversion unit as a prototype,a method of designing all-phase covered chiral structure LP-to-LP polarization conversion units was proposed by combining several similar structural units.Using this method,one group of the all-phase covered chiral structure LP-to-LP polarization conversion units which working at 9GHz was designed by combining three kinds of elements with similar structures.Based on this,an 8-unit phase gradient metasurface was constructed,and its function was verified by simulation and experiments.The results show that the designed function of it was realized,which proves that the all-phase covered chiral structure LP-to-LP polarization conversion units designed in this thesis is reasonable.At the same time,two kinds of linearly polarized wave to circularly polarized wave(LP-to-CP)polarization conversion units with asymmetric and symmetric structures were designed by adding the numbers of splits on the SRR LP-to-CP polarization conversion unit,and their functions were also verified by experiments.The results show that they have good polarization control performance,and the expected design target is achieved.(2)Based on the numerical calculation results of the radiation phase of the source antenna,four kinds of lens antennas were designed by using the all-phase covered chiral structure LP-to-LP polarization conversion units,including a monofocal planar wave lens antenna,a bifocal plane wave lens antenna,a Bessel wave lens antenna and a Bessel beam deflecting lens antenna,and their performance was simulated and verified by experiments.The results show that the designed antennas have good impedance matching and radiation characteristics,and the practical application requirements can be met.(3)A high-gain CP antenna was designed by combining the symmetric structure LP-to-CP polarization conversion unit with a Fabry-Perot cavity antenna,and its performance was verified by experiments.The measurement results show that the working bandwidth and the maximum gain of the CP antenna are 0.63GHz(8.71-9.34GHz)and 18.3d Bi respectively,and the expected design target is achieved.(4)Six kinds of basic units that can be used in the design of wideband anisotropic artificial electromagnetic medium polarization converters were studied systematically,including metal strip,slit metal strip,metal ring,split metal ring,thin metal wire and dielectric plate.Then,four novel anisotropic artificial structure arrays were designed by combing these basic units,including metal strip and slit metal strip hybrid array(MSSMSHA),metal wire array(MWA),metal wire and dielectric plate hybrid array(MWDPHA)and metal strip and split metal ring hybrid array(MSSMRHA).Based on the mentioned artificial structures,several polarization converters with different functions were designed successfully.The work proves that the method of combining various basic units to design different polarization converters is feasible.In addition,to solve the problem of the functions in the passive polarization converters can not be adjusted,a new type reconfigurable active polarization converter was designed by combining PIN diode with anisotropic artificial structure unit.In the frequency band of 2-3GHz,it can realize the conversions between any two kinds of polarization waves among of u-polarization wave,v-polarization wave,left-handed circular polarization wave,right-handed circular polarization wave.The obtained research results in this thesis can provide reference and guidance for the future design and application in the field of antenna about high-performance chiral artificial structure LP-to-CP polarization conversion units,all-phase covered chiral structure LP-to-LP polarization conversion units and broadband anisotropic artificial structure LP-to-CP polarization conversion units. |
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