Researches On Electromagnetic Scattering Algorithms Based On Integral Equation

In the paper, the new electromagnetic scattering algorithms have been introduced-Recursive Aggregate T- Matrix Algorithm (RATMA) and Fast Multipole Algorithm (FMA). Two kinds of methods are precise and efficient and have advantages over conventional method of moment in computational speed and requirement for storage space. It is emphasis how to calculate three-dimensional radar cross section (RCS) by the FMA because of its superiority. The universal program has been accomplished by the FMA, which may calculate the radar cross section of all kinds of shapes three-dimensional conducting bodies. In Chapter 1 the definition of RCS is introduced and discusses the recent development of the computational electromagnetics. The RATMA can calculate the electromagnetic scattering of multiple cylinders, and can be used in remote sensing. In Chapter 2 simply derivation of the RATMA is given by the addition theorem, and the general T matrix of single cylinder is deduced. The worked out examples show the effectiveness of the RATMA in the analysis of the scattering field of single cylinder or multiple cylinders. The FMA need the high order Hankel function, In Chapter 3 the algorithm of calculating the high order Hankel function of the second kind is discussed. Because of the low effectivity and unsteadiness to use the recursive algorithm to calculate the high order Hankel function of the second kind, the paper introduces a kind of new fast algorithm to solve the problem. The worked result indicates: The new fast algorithm is a kind of precise algorithm. In Chapter 4 windowed function of data signal processing is introduced and applied to addition theorem, which succeeds in solving the difficult problem: it has a bad result when recursive T -matrix is applied to calculate the wave scattering of electrically large objects and multiple objects in the excitation of TE wave. Another mode of the total T matrix is derivated from the integral equation. Finally the calculation result of two dielectric cylinders proves the effectiveness of windowed function and the correctness of the expression of the total T -matrix. Windowed function is also applied into FMA, which can accelerate the computation speed of the FMA. The FMA equation of three-dimensional conducting body is derivated in the Chapter 5. We choose polygonal plates to construct the shape of realistic structures. The program is complete ,which can calculate the RCS of all kinds of shapes three-dimensional conducting bodies. Regarding the geometry parameters of the polygonal plates as the geometry inputs, the program segements every plate into modes automatically. Overlap modes can be obtained between the connecting intersecting plates. The results of calculating RCS for several typical and complex three-dimensional conducting bodies are obtained. Finally the paper emphatically introduces the MLFMA (multilevel fast multipole algorithm). Based on hybrid field integral equation the formulation of computation for the electromagneticscattering of three-dimensional object is derivated. Then the optimization of invariant terms and the expression of every child cube is analyzed during the electromagnetic scattering calculation when using the MLFMA.