Time Domain Inverse Scattering of 2-D Perfect Conductors by Genetic Algorithms
| Autor: | Chung-Hsin Huang, 黃中信 |
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| Rok vydání: | 2004 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 92 In this thesis, an FDTD-based time domain inverse scattering problem is investigated. A global optimization scheme based on genetic algorithm is used to reconstruct the microwave image of various imbedded objects, which are buried in a three-layer stratified material medium. Assume a perfect conductor cylindrical object is buried in the middle layer of a three-layer stratified material medium, such as a metal pipe in a concrete wall. The Gaussian line source located in the first medium (air, for example) is used excite to illuminate the problem space, and then the scattered electric fields are measured in the same medium. In order to more effectively describer an unknown cylinder with arbitrary shape, the shape function is expanded in terms of the spline functions other than Fourier series normally used. In order to model the cylinder shape more smoothly subgridding technique is implemented. The genetic algorithm is then used to convert the inverse scattering problem into an optimization one. The measured scattering E fields are compared with the calculated E fields obtained by a home-made FDTD code. When the time domain waveforms of the two fields are getting closer, it means the reconstructed object is converging to the original one. The genetic algorithm (GA) is global optimization emulation the natural evolution procedure — survival of the fitness. The main advantage of the GA is to overcome the convergence to local minima as the traditional optimization schemes usually do. Therefore, even the initial guesses are far from the real solution, the object properties such as position and shape can be reconstructed successfully. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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