Analysis Of Electromagnetic Waves Cattering From Object With Complex Media And Coated Structures

In the field of radar for space exploration, satellite-to-ground communications and radar targetrecognition, the study on the electromagnetic scattering properties of the target has a very importantsignificance. In this dissertation, we focus on the simulation technique of general dielectric andobjects coated with dielectric based on the numerical simulation tool-method of moments (MoM).The author’s major contributions are outlined as follows:1. Electromagnetic scattering properties of bi-anisotropic materials and objects coated withbi-anisotropic materials are researched. Firstly, the volume Integral Equations (VIE) is proposed forthe analysis of the electromagnetic scattering characteristic of bi-anisotropic materials and thecorresponding discrete formulae are deduced. The applied fields of equivalent dipole-moment method(EDM) are then extended. On this basis, for complex bi-anisotropic media, a new method——bi-anisotropic fast dipole method (BI-FDM) is then proposed to analyze scattering from manykinds of media including anisotropic, bi-isotropic/anisotropic, chiral media and so on. In addition, thechiral double negative media and chiral nihility media as two special materials, the MoM-basedBI-FDM is then first used to analyze the characteristics of electromagnetic scattering of the two kindsof materials. Furthermore, volume-surface integral equations (VSIE) are proposed for the analysis ofthe electromagnetic characteristic of bi-anisotropic materials and coated objects. The BI-FDMcombined with EDM is then extended to analyze the electromagnetic scattering characteristic ofbi-anisotropic media and coated objects. Numerical results show that the presented method is valid.2. Electromagnetic scattering properties of left-handed materials (LHM) are researched. Surfaceintegral equation (SIE) is proposed for the analysis of the electromagnetic scattering characteristic ofLHM. According to the feature that the SIE formulation at perfectly matched LHM–RHM interfacehas stability problem, a preconditioning method which the imaginary parts of the dielectric parametersare artificially added a small amount of loss is applied to overcome the disadvantage of slowconvergence or divergence effectively. In addition, the first attempt is presented to apply the VIE toanalyze the electromagnetic scattering characteristic of LHM. Preconditioning techniques areconstructed for the poor behavior of the impedance matrix. And then the distributions of eigenvaluesbefore and after preconditioning are discussed, respectively. Numerical results show that theiradvantages and disadvantages of the SIE and VIE for the LHM and RHM.3. Electromagnetic scattering properties of high-constrast materials and objects coated withhigh-constrast materials are researched. Firstly, general volume-surface integral equations (GVSIE) are formulated by combining the Poggio, Miller, Chang, Harrington, Wu, Tsai (PMCHWT) and VIE.The corresponding discrete formulae based on the GVSIE are deduced. On this basis, theEFIE-GVSIE is formulated for high-constrast materials coated bodies. Electromagnetic scattering ofhigh-constrast materials and objects coated with high-constrast materials are analyzed for using theintegral equations combined with EDM and adaptive cross approximation algorithm (ACA). Based onthe form of equivalent volumetric electric/magnetic currents and surface electric/magnetic currents, asimple and effective preconditioning method is presented to improve the behavior of the impedancematrix. Numerical results show that the GVSIE can reduce the unknown number significantly. TheGVSIE combined with EDM/ACA and the preconditioning technique can save the CPU time and thememory requirements significantly. The computational efficiency is then improved significantly.4. Electromagnetic scattering properties of thin dielectric and thin bi-isotropic materials areresearched. Firstly, the full current equivalent model of isotropic thin dielectric sheet (TDS) isdeduced. In the equivalent model, the electric displacement vector is decomposed into tangential andnormal components. The modified RWG basis is employed for the tangential component of theelectric flux, and the pulse basis is used for the normal component. Secondly, a bi-isotropic TDSequivalent model is proposed to analyze the electromagnetic scattering of thin chiral materials whichis classified to bi-isotropic materials. The method is verified correct by comparing with the VIEmethod. Numerical results show that the method can reduce the unknown number significantly, andthen improve the computational efficiency.Finally, some conclusions are drawn and future work is proposed.