LARGE accurate modeling of complex stealth targets , and fast algorithm
|School||University of Electronic Science and Technology|
|Course||Electromagnetic Field and Microwave Technology|
|Keywords||Multilevel fast multipole method Electromagnetic Scattering Large target Parallel algorithms Fast iterative method Radar cross section|
With the continuous development of microwave technology, its application in the fields of communications, radar frequency. Therefore, the analysis of the electromagnetic characteristics of the Radio and TV, the Extremely Large size target becomes more important. As the solution of the electromagnetic scattering and radiation problems fast algorithm one multilevel fast multipole method for its high accuracy, to solving low complexity, to become one of the primary means of analysis of the scattered radiation of electrically large. From fast multipole method and the multilevel fast multipole pole on the principle of the method, the focus on the means to optimize the parallelization of the multilevel fast multipole method, solving efficient large target pre-conditions and fast iterative method, and step to study the application of the method in the calculation of the radar cross section. This article first briefly integral equations in electromagnetic scattering problems and numerical methods for solving such equations - method of moments, through the study of the basic principles and key technologies, the use of numerical methods for solving the problem of electromagnetic scattering concrete steps. Second, detailed study of a fast algorithm for solving integral equations - multilevel fast multipole method. Departure from the method of mathematical principles on the use of its concrete steps for solving integral equations and related optimization, and efficient parallel strategy research. In this paper, the maximum equivalent distance method to reduce the multilevel fast multipole and pole method layers mode number, does not affect the accuracy of the premise, effectively saving computation time and memory consumption. And verify the correctness of the procedure by comparison with analytical solutions and scaling values. Again, TVU and Extremely Large target electromagnetic scattering problems in solving the pre-conditions and fast iterative method related research, sparse approximate inverse preconditioners (SAI) in the parallel multilevel fast multipole method. On this basis, the use of three different Krylov subspace iteration method - GMRES, Bi-CGSTAB and flexible GMRES algorithm on the different types of large target, and the target type, given the choice iterative method recommendations. In the fifth chapter, based impedance boundary condition (IBC) on the thin coating goal electromagnetic scattering problem. In this chapter, the first analysis of the scope of application of the impedance boundary condition, derived based IBC integral equation expressions given multilevel fast multipole method implementation. By analytical solution and the comparison of the measured values, inspection of the accuracy of the procedure. Finally, we study the Extremely Large size high quality meshing. Use objectives geometric symmetry of nature, rely on the means of re-subdivision algorithm to achieve high quality subdivision of the grid, and laid the foundation for solving the ultra-large target for accurate electromagnetic scattering problems. To display the program's ability to solve the calculated 300 wavelengths in diameter, an unknown amount of over 110 million metal ball scattering problem, and the root mean square error of the analytical results is only 0.527dB. In order to test the program's ability to solve practical engineering problems, this paper calculated stealth aircraft - F117 vfy-218 single of the two models, the bistatic radar cross section calculated numerical cases the maximum electric size more than 660 wavelengths, unknown up to 47 million, shows the procedure for solving ability and accuracy, and succeeded in solving some practical engineering needs.