Study On Targets Scattering Characteristics Of Vortex Electromagnetic Waves Based On High Frequency Method

Due to the special physical property of Orbital Angular Momentum(OAM),the wavefront phase distribution has a complex spiral structure and has different electromagnetic scattering characteristics compared with the traditional plane waves.Therefore,in recent years,research on the target scattering characteristics of vortex electromagnetic waves has been carried out and gradually become a research hotspot.In this thesis,based on the high-frequency method of electromagnetic scattering,combining the vortex electromagnetic wave with the high-frequency method to investigate the generation of vortex electromagnetic wave based on Uniform Circular Array(UCA),the amplitude and phase characteristics of vortex electromagnetic wave front,and the scattering characteristics of vortex electromagnetic wave based on various targets,especially the electric large-size targets are studied in depth,and the target imaging of vortex electromagnetic waves is explored initially.The main research contents of this thesis are as follows:Firstly,the theory and research methods related to vortex electromagnetic waves.The basic theory of vortex electromagnetic wave is introduced in detail,and on this basis,the basic principle of vortex electromagnetic wave generation by two-dimensional antenna arrays is studied.The OAM spectra obtained by using the spectral analysis theory can accurately and completely present the modal number information of the vortex electromagnetic waves,which lays the foundation for the subsequent research on the scattering characteristics of the vortex electromagnetic wave target.Secondly,the amplitude phase characteristics of the vortex electromagnetic wave front based on the high-frequency method are studied.First of all,the basic principle of high-frequency method and the radiation characteristics of ideal dipole are introduced,and the ideal dipole is used as the array element of two-dimensional antenna array,and the vortex field source is combined with high-frequency method through geometric and electromagnetic parameters,and the vortex electromagnetic wave scattering modeling method based on high-frequency method is proposed,so that the electromagnetic scenes applicable to various targets and arbitrary array configurations can be built.Then,based on the electromagnetic dipole UCA array and the high-frequency method,the amplitude phase distribution of the vortex beam under the influence of different parameters are simulated and analyzed,including the influence of the array radius,the number of array elements and the array operating frequency on the zero-value region in the center of the ideal vortex beam,as well as the influence of the phase blurring degree of the wavefront phase distribution and the vortex radius size.The effect of the array radius and array operating frequency on the zero-value region of the ideal vortex beam center,the degree of phase blurring in the wavefront phase distribution,the vortex radius,etc.In the end,the OAM spectrum is used to analyze the effect of target size and position on the perturbation of the radiation field.Thirdly,the scattered field characteristics of vortex electromagnetic waves based on high-frequency methods are studied.In the begining,the definition method of OAM Radar Scattering Cross Section(ORCS)is introduced,enables the scattering capability of the vortex EM wave-based target obtained by the high-frequency method to be quantified.Then,a suitable electromagnetic calculation scenario is built using the high-frequency method with definable dipole arrays.The scattering effects of simple targets,combined targets,and electrically large targets are investigated for each modal number of vortex electromagnetic waves.And analyze the amplitude phase distribution,OAM spectra and OAM radar scattering cross-sectional area fluctuation trend of each target under the influence of different factors.The scattering characteristics of vortex electromagnetic waves under different targets are obtained.Finally,the basic principles of vortex electromagnetic imaging are introduced,based on the relevant imaging process and imaging model,the electromagnetic vortex imaging of the ideal point target is realized.And the scattered echoes of general targets are also obtained based on the high frequency method of definable dipole arrays,for a preliminary study and analysis of vortex imaging of general targets.In this thesis,we analyze and study the target scattering characteristics of vortex electromagnetic waves based on high frequency method.It further provides a simpler and applicable method for modeling and calculating the scattering of vortex electromagnetic waves in various electromagnetic environments.The scattering characteristics of simple and general targets are also discussed.It also discusses the scattering characteristic laws including simple targets and general targets,and expands the research of vortex electromagnetic waves in the field of electromagnetic scattering.