The Cg-fft For Electromagnetic Scattering And Radar Imaging Technology,

The scattering of targets has gained great attention in the subject of electromagnetism.On one hand, it is necessary to solve these problems more properly to further develop electromagnetism itself. On the other hand, as new technologies appear, the requirements of calculating complex structures, large-scale scattering problems are booming. Recently, with the rapid development of computer, the scattering problems which couldn't be solved by analytical methods previously, now can be solved by numerical methods. After R.F. Harrington presented method of moments (MOM) in 1968, all kinds of numerical methods have been invented one after another to help calculate large problems more quickly and more accurately.Conjugate Gradient Fast Fourier Transform (CG-FFT) method is a fast iterative method which is used to solve large linear equations. It was invented in the 1980s. This dissertation describes the basic principle of CG method and analyzes it's convergence in which the formulation related to the rate of the convergence is also deduced. Meanwhile, the theory and the application in solving products between Toeplitz matrices and vectors of FFT arithmetic is also referred in the dissertation. Based on all the above, CG-FFT method is used to calculate the following problems in turn: the radiation of a thin wire antenna, the scattering of a perfectly conducting strip perpendicularly illuminated by a plane wave and the scattering field of a metal square plate in the presence of a dipole antenna. By the way, the unknown quantity of the integral equations arising in these problems is the equivalent density of current. The numerical results gained by CG-FFT method are compared with analytical solutions. Excellent agreements can be observed. So the accuracy of CG-FFT method is proved. Besides, the curves about the normalized residual error varied with iterative number are presented to verify the convergence of this method. CG-FFT is an efficient method due to its shorter calculating time and less computer memory, and will be of helpful for scattering analysis and detection of more complex single or multi-targets.Radar imaging is another topic of this dissertation, including one-dimension and two-dimension imaging parts. It will make engineers observe and research the scattering rule instantaneously and directly using Range-Doppler (R-D) arithmetic. The simulation of a sphere and a model of missile is presented to prove that R-D arithmetic is feasible here.