| 1 introductionThe use of all kinds of electrical devices make up of a complicated electromagnetic environment. Researching the radiation of electrical devices and their work state under complicated environment is an important field of electromagnetic compatibility (EMC) subject. In the analysis of EMC problems, electrical system always working in complicated environment, and their shapes and structures are often complicated too. Due to the electrical large object which have irregularity in shapes and various kinds of components including lots of materials and forms like holes, slots, intracavities and loads, the analysis process is always influenced by complex electromagnetic physical process and system structure. Facing this, not only analytic method but also experimental media could not generally solve modern EMC problems, even less economy cost. From point of field, adopting modern computational electromagnetism (CEM) as a method is a proficient solution. In this paper, the radiation from commonly used devices and their effect caused by extern field is solved from the point of view of field.2 time-domain CEM methodTo the analysis of EMC problem, time domain method is more and more important in many numerical computation methods. It is because that it can provide prescription in not only time domain (which is the straight and convenience) but also single frequency domain. For increasing the efficiency and satisfying kinds of needs, one can get better precision and faster rate of computing by adopting advanced technology like parallel computation and domain decomposition algorithm.Computer is used to realize the simulation of EM problem, so first, methods such as method of moments, fast multiple multipole method and finite element method commonly used to analyze these kinds of problem are introduced briefly. And then finite-difference time-domain (FDTD) method and pseudo spectral time domain method are both excellent solutions to analyze EMC problem, using them one not only can get the distribution of power density and contour of frequency spectrum of the field radiated by electrical devices but also can research the effect arisen by extern field. It's basic theory and relative useful techniques are presented in detail in chapter 3.The two methods are discussed through comparing with each other, starting from general principal of differential equation. We detailedly present the basic principle, stability condition, absorbing boundary condition, numerical dispersion error, and running time and efficiency of the FDTD and PSTD algorithm, particularly expatiate basic principle and application of single domain Fourier PSTD (FPSTD), through the comparison with FDTD, one can get that FPSTD have a smaller numerical dispersion error and more advanced computation efficiency thus is fit to electrical large objects. Besides these, non uniform FFT (NUFFT) is discussed id the end.3 Parallel computation technology and domain decomposition algorithmParallel computation technology is a modern computation technology, it have got many achievements in various research and projects. Parallel means that one and more things can proceed in one time segment even at the same time. Lots of numerical modelings and simulations of scientific research and projects adopt this kind of technology which has many processes communicating by transferring message with each other.The specialty of domain decomposition algorithm is that it can decompose the computation domain into many sub computation domains which let the sub computation domains as regular as possible, and then one can compute the problem in regular sun domains. For the recent 20 years, with the fast development of modern computation technology, domain decomposition algorithm is now gradually becoming one of the best ways to solve large and complex problems.We present the principal, design method, algorithm and performance measurement of parallel computation in Chapter 4, then compile a program which is used to get the number ofπin the MPICH software environment to express the concrete concept of parallel computation. And in chapter 5, we present the detailed principles in solving Laplace equation, Helmholtz equation and Maxwell equation respectively.4 Domain-decomposition parallel multiple PSTD (MPSTD) algorithm and its application in analysis of EMCThe above Fourier and Chebyshev PSTD methods are for a single computational domain; they are ideal for smoothly varying materials where no discontinuities are present in the material properties and thus the field components. Although these methods can also be applied to discontinuous materials, the accuracy is no longer spectral. Therefore, if there are sharp material discontinuities, a better way is to use the multidomain PSTD method. This will have an additional benefit of removing staircasing errors associated with the tensor product of 1-D grids that are inherent to the single-domain PSTD methods. Though MPSTD has a little big amount of computation because it requiresπgrids per wavelength, too many references supported that MPSTD is much better than FDTD in EM especially in EMC problem.Based on the discussions in these chapters, we put up three experiments and numerical computations by various domain decomposition and parallel MPSTD and FDTD algorithms to be compared; first, leads crosstalk is a quite complex problem in EMC, comprehension of the EM field around the lead is important to the analysis of crosstalk; second, to simulate a radiated EM field of a board shape vibration generator base station antenna; third, to compute the system EMC safety margin of an automobile in order to substitute the test method .In conclusion, good agreement between the calculated data using time domain method and data from references prove that time domain methods are effective ways in the analysis of EMC problem; they will he used more widely. |
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