On High Performance Numerical Algorithm For Electromagnetic Scattering And EMC Analysis

Low observable technology of radar band and its counter technology have been developed in recent years. There are several kinds of stealthy targets for present radar systems have been applied in actual war. The study on electromagnetic scattering feature of target is a very important research direction in the field of electromagnetic field and microwave technology, but the appearances of new style targets have put forward higher requirement to corresponding researches. Modern war require targets not only have low observable feature but also have the ability of transferring information in any where and at any time. A large quantity electric and information devices are integrated on targets to upgrade the electronic and information degree of targets. The different devices on target, especially the antenna systems always cause electromagnetic compatibility(EMC) problem, so the EMC analysis of antennae on electrically large target is also a important study subject. According to the demand of engineering and new research progress, this dissertation makes deeply insight to the high performance algorithms for the electromagnetic scattering and EMC analysis of electrically large target. The author's major contributions are as follows:1. An adaptive multilevel fast multipole algorithm(AMLFMA) and its parallel algorithm for the analysis of metallic targets are presented. In this algorithm, the integration calculation of the traditional multilevel fast multipole algorithm(MLFMA) can be simplified and all the transformation procedure can be calculated by fast Fourier transformation(FFT) by expanding the basis functions and testing functions with Dirac functions on different position, some other improvement methods are also used in this adaptive fast algorithnm. The parallel algorithm of AMLFMA algorithm is introduced simultaneously and the parallel AMLFMA algorithm can solve more large scale problems.2. The adaptive multilevel fast multipole algorithms and corresponding parallel algorithms for the analysis of homogeneous medium targets, coated targets and composite targets are presented also. The combined field integration equtions(CFIE) for the medium surface and composite medium surface are established first. While solving the corresponding CFIE by using AMLFMA algorithm the adaptive fast computation methods are applied in far and near field mutual action processes, translation and disaggregation process, so the algorithm efficiency is improved significantly. The parallel algorithms of AMLFMA for homogeneous medium targets, coated targets and composite targets are introduced and some simulation examples of radar cross section(RCS) analysis and antenna EMC analysis of electrically large plats are presented.3. An element level finite element method(ELVFEM) and its parallel method are presented. The ELVFEM can calculate the multiplication of matrix and vector on element level and no need to form the global coefficient matrix, so the CPU time and memory can be reduced. The parallel method of ELVFEM is discussed also.4. For the analysis of inhomogeneous medium, a fast finite element-boundary integration(FE-BI) algorithm via ELVFEM and AMLFMA and its parallel algorithm are presented. The efficiency of this fast FE-BI algorithm is improved significantly. According to the parallel algorithms of AMLFMA and ELVFEM, the parallel fast FE-BI algorithm is presented. The electromagnetic scattering feature and antenna EMC feature of coated targets are analyzed by using serial and parallel fast FE-BI algorithms. The numerical results proved the effectivity of the algorithms presented.5. Fast wide band algorithms and corresponding parallel algorithms are presented. Combining asymptotic waveform evaluation technique (AWE) with AMLFMA and ELVFEM, the corresponding wide band algorithms for solving wide band electromagnetic problems of different targets can be obtained. To solve lager scale problems, the parallel algorithms of different wide band algorithms are discussed. Numerical results proved that all the presented methods are effective and accurate.6. The MLFMA expressions of wire-surface structure on conductor, medium, and composite target are presented first and some key parameters are determined for antenna EMC analysis. Both the importance of the parameters and their association are discussed. Some analysis models of antenna EMC are established, the models include far field model, isolation(coupling) model, interference power model and antennae arrangement optimization model. The solution methods of the presented models and the flow of antenna EMC analysis are discussed simultaneously. In engineering practice, the antenna EMC features of different plats, such as vehicle, airplane, ship and satellite systems, were analyzed by using the fast algorithms and their parallel methods presented in this paper.