Research On Electromagnetic Scattering And Interaction Of Anisotropic Targets

Many materials in nature,such as magnetized plasma,exhibit the electromagnetic anisotropy.In addition,there are many synthetic anisotropic materials,such as signal elements in optical signal processing.These anisotropic materials can affect the scattering cross-section of radar targets,and are widely used in radar antenna shield and baseband of microwave transmission band antenna.In the key technology of national defense,anisotropic materials are often used in stealth design of targets.Therefore,the research of electromagnetic scattering of the anisotropic targets and their interaction has become a hot topic in the domain of electromagnetic scattering.In this dissertation,the electromagnetic scattering characteristics and electromagnetic interaction among anisotropic targets under plane wave irradiation and beam irradiation are studied.The main research contents and innovations of this dissertation are as follows:1.The scattering characteristics of anisotropic targets irradiated by the plane E.M.wave are studied.The analytical solution of scattering of anisotropic medium targets under the irradiation of the plane wave is derived.The scattering characteristics of plasma and lossless anisotropic targets are discussed.Aiming at the theoretical bottleneck of scattering from anisotropic medium,and based on the uniqueness theorem of electromagnetic field,an innovative method of equivalent the anisotropic medium as the isotropic medium is proposed.By calculating the equivalent propagation wave number in the anisotropic medium,the numbers of wave number are reduced reasonably,and the analytical solution of scattering field is obtained.At the same time,the method of reconstructing the parameter tensor of lossless anisotropic medium,a symmetric tensor,to the diagonal tensor is proposed.The analytical relationship of electromagnetic field before and after the reconstruction of parameter tensor of lossless anisotropic medium is discussed,which provides a theoretical method for studying the scattering of arbitrary lossless anisotropic medium.2.The scattering characteristics of the spherical anisotropic medium targets irradiated by the beam are researched.The analytical solution of the spherical anisotropic target in the E.M.wave beam is derived.The expansion formulas with the spherical vector wave functions of zero order,first-order and second-order terms of Taylor series are presented,and the analytic expressions of the coefficients of each expansion are obtained.This method can effectively reduce the difficulty of calculation.By expanding the elliptical Gaussian beam with Taylor series,the scattering characteristics of a spherical anisotropic medium target and its coated target illuminated by the elliptical Gaussian beams are studied.Taking gypsum crystal as an example,the scattering results are simulated and the effects of beam parameters and target size on scattering characteristics are discussed.3.The scattering characteristics of a cylindrical anisotropic target irradiated by a beam are researched.By using the orthogonality of cylindrical vector wave function,the concrete method of expanding arbitrary electromagnetic beam with cylindrical vector wave function is proposed and its analytical expression is given.The scattering characteristics of a finite length anisotropic cylinder and the cylinder coated with anisotropic medium are analyzed.The scattering characteristics are simulated,and the factors affecting the scattering characteristics are discussed,and the physical mechanism of these phenomena is analyzed.4.The electromagnetic interaction and scale measurement of anisotropic targets are studied.A mathematical algorithm is proposed which may be used to study the electromagnetic interaction of targets.The electromagnetic interactions between spherical anisotropic targets,cylindrical anisotropic targets,spheres and cylinders are studied,and the law of interaction is obtained.A novel theory of scaling measurement the electromagnetic scattering for dielectric targets is proposed,and the steps of scaling measurement in microwave anechoic chamber are given,and the effectiveness of the proposed method is verified.This method has good security and low cost,and can be used to obtain radar characteristics of land tanks,ships and space vehicles.