Research Of The Electromagnetic Scattering Characteristics Of Electrically Large Objects Based On Characteristic Basis Function Method

The problem of electromagnetic scattering is an important researchdomain in engineering electromagnetics. With the frequency increasing andthe wavelength decreasing, the original objects become electrically large. Soit is important and practical to study the electromagnetic scatteringcharacteristics of electrically large objects. A basic idea of analyzing theelectromagnetic scattering characteristics of electrically large objects istransforming the large problems into some small problems by dividing thelarge objects into a number of small regions, then the surface current andradar cross section (RCS) can be computed fast. Characteristic basis functionmethod (CBFM) is a novel approach for the efficient solution ofelectromagnetic scattering problems. The mutual coupling effects amongdifferent subdomains are included directly by constructing the high level basisfunctions, referred to herein as primary and secondary characteristic basisfunctions (CBFs), which are used to represent the unknown induced currents onthe blocks. The dimension s of coefficient matrix in the method can also becontrolled by selecting the size of subdomains, and the matrix size can be reduceddramatically. Then these CBFs can be solved by the Galerkin method rather thaniterative method.In this thesis, the theory of method of Moment (MOM), the basic functions andtesting functions are introduced firstly, the steps to compute the radar cross section ofconducting cylinders and dielectric cylinders are also elaborated. Secondly, the theoryof CBFM and how to analyze the electromagnetic scattering characteristics ofelectrically large objects using it is introduced. Then the presented method is used tocalculate the current distribution and the radar cross section from two dimensionconducting cylinders, square cylinders, square cylinders with slot and dielectricsquare cylinders. Finally, the method is used to analyze the electromagnetic scatteringcharacteristics from three dimension electrically large dielectric objects.The systematical analysis is given for the electromagnetic scatteringcharacteristics from two-dimensional and three-dimensional electrically largeconducting cylinder and dielectric cylinder using CBFM for the first time in thisthesis. The discontinuity of the induced current resulting from the partition of the geometry directly is eliminated by extending the boundaries of the subdomains. Thenumerical results obtained by the presented method are in good agreement with thatachieved by the traditional MOM, while the computational efficiency is improvedconsiderably.The investigation is very useful not only in further studying theelectromagnetic scattering characteristics of complicated large objects, butalso in improving and designing the wide-band radar, ultra wide-band radar andnew wide-band radar absorbing material.