| In recent years,metamaterials has been a hot topic in both electromagnetic theory research and engineering applications.Metamaterials is a sort of artificial composite structure which composed of conventional electromagnetic materials,generally meet a particular arrangement,and ultimately achieves the extraordinary characteristics that has not yet been found in nature or in ordinary materials.With the research getting further,metamaterials is not only a physical structure but also a new concept,which opens a broader research space for the classic electromagnetic theory.People can change the basic unit form and spatial arrangement of the metamaterial to obtain a special property of the electromagnetic medium,and then design a variety of new high-performance microwave,millimeter wave,terahertz wave devices and systems.Research of this thesis is based on the deep understanding of the electromagnetic properties of metamaterials,be driven by the engineer application of the metamaterials,starts from the application of the metamaterials on antenna design,electromagnetic wave polarization regulation and scattering control,carries out a systematic research on the fundamental theory and key technique study of the metamaterials,therefore provides theoretical exploration and practical reference for the development and application of metamaterials.The main contents of the thesis are as follows:1.The basic theory of anisotropic media and electromagnetic waves scattering is studied.To begin with,the metamaterials polarization transformation structure design is proposed,and the theory of polarization transformation of anisotropic media is mainly studied,including the concept of anisotropic media,the mechanism of polarization transformation and the analysis method of anisotropic material.And the conditions of the polarization transformation when the electromagnetic wave passes through the anisotropic medium are summarized.Then,the method of extracting the equivalent constitutive parameters(including the equivalent dielectric constant,permeability,refractive index and characteristic impedance)of the anisotropic metamaterials is analyzed,and the effectiveness of the algorithm is evaluated by calculating the constitutive parameters of the F4 B dielectric plate.In addition,from the radar equation,the basic concept,main features and representation of radar cross section are studied and analyzed.2.Based on the "single negative" characteristic of the complementary split ring resonantor,the antenna impedance bandwidth is broadened.By analyzing the split ring resonantor,the complementary split ring resonantor,and the equivalent circuit of microstrip transmission line with complementary split ring resonantor,the special resonant performance and the "single negative" performance are studied.The working principle and design method of the integrated balun printing dipole antenna is summarized,and then the complementary split ring resonantors are loaded at the feed point of the printed dipole antenna,which forms the broadband and dual polarized printed dipole.The measurement results show that the antenna has a return loss of less than 10 d B in the frequency range of 1.02 GHz ~ 2.03 GHz,and the relative bandwidth is basically one octave.The impedance characteristic of the complementary split ring resonantor,is equivalent to a negative dielectric constant band-stop filter,suppressing the high-order resonance of the antenna at about 2GHz,improving the impedance characteristic of the antenna at low frequency and increasing the impedance bandwidth of the antenna by more than 10%.3.Based on the broadband dual polarization printed dipole with complementary split ring resonantors,two methods are used to improve the gain of the antenna.Initially,the concept of "log-periodic parasitic directors(LPPDs)" are firstly proposed,and they are loaded on the front end of the dual-polarized printed dipole,thus increasing the antenna gain by 3.7d B.Then,the split ring resonantors arrays are loaded at the front end of the dual-polarized printed dipole,forming directors with special function in the end direction of the antenna,increasing the gain by 4.11 d B.In both methods,the antenna impedance bandwidth is about 70%,and the profile of second design of the antenna reduced by 12% than the first one.4.In order to control the polarization state of the electromagnetic wave,the polarization transformation characteristics of anisotropic metamaterials are utilized.A X-band periodic metal line polarization converter is designed firstly,which can be used as a radome to achieve the circularly polarized radiation on the pyramid.The measurement results show that the design achieves return loss RL <10d B and antenna ratio AR <3d B within the 7% bandwidth,and the radome has little effect on the antenna radiation pattern.Secondly,a broadband,reflective linear polarization rotator based on anisotropic metamaterials was designed by using the idea of multiple resonance.It can rotate a linearly polarized wave with a specific angle by 90° within a wide operating frequency band,so that the reflected wave is orthogonal to the incident wave polarization.When the electromagnetic wave is incident vertically,the structure achieves a polarization conversion of more than 90% in the frequency band of 8.41 GHz to 11.3 GHz.The simulation results also show that the polarization conversion is still greater than 60% when the incident angle is gradually increased to 50°.The structure uses a flat design,simple structure,the overall thickness of only 1.6mm(about ?/20).5.A metamaterials low RCS reflection plane based on the principle of phase cancellation is designed by using the idea of "encoding metamaterials".Compared with the PEC reflection plane with the same size,the design has a RCS reduction greater than 10 d B in the 7.85GHz~10.35 GHz frequency band,and a good RCS reduction effect for different polarized incident wave in a wide angular area. 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