利用基因法則及TE極化波照射重建部份掩埋完全導體之研究

本論文探討基因法則應用於二維物體之逆散射問題。我們針對物體照射TE極化波的情況下，就在兩半空間中完全導體的逆散射進行探討。對於完全導體而言，電磁波在完全導體表面之總電場的切線分量為零。因此我們利用完全導體表面電流的概念，可導出一組非線性績分方程式，利用該方程式，我們可以從中得到該物體的散射場資訊。此一步驟為正散射問題。對於逆散射部份，我們引進了基因法則(Genetic Algorithm)。利用基因法則時，我們適當的選取參數，同時結合所求的正散射公式，由此即可求出散射場的相關資料，藉以求得此二維物體的形狀函數。不論初始值的猜測值如何，基因法則總會收斂至整體的極值(global extreme)，因此，在數值模擬顯示中，即時最初的猜測值與實際值相距甚遠，最終我們依然可求得準確的數值解，成功的重建物體形狀函數。而在數值模擬顯示中，量測的散射場即使加入高斯分佈的雜訊，依然可以得到良好的重建結果，研究證實其有良好的抗雜訊能力。

關鍵字

穩態基因演算法；完全導體；動差法；部分掩埋； TE極化波

並列摘要

In this paper, we present a computational approach to the imaging of a partially immersed perfectly conducting cylinder by the steady-state genetic algorithm. A conducting cylinder of unknown shape scatters the incident transverse electric (TE) wave in free space while the scattered field is recorded outside. Based on the boundary condition and the measured scattered field, a set of nonlinear integral equations is derived and the imaging problem is reformulated into an optimization problem. An improved steady-state genetic algorithm is employed to search for the global extreme solution. Numerical results demonstrate that, even when the initial guess is far away from the exact one, good reconstruction can be obtained.

並列關鍵字

Steady-State Genetic Algorithm ； Perfect conductor ； Moment Method ； Partially immersed ； TE wave

參考文獻

[1] A. G. Ramm, "Uniqueness result for inverse problem of geophysics: I,"Inverse Problems, vol. 6, pp. 635-641, Aug. 1990.

[2] H. P. Baltes, Inverse scattering problems in optics. New York: Springer-verlag Berlin Heidelberg, 1980.

[3] M. M. Ney, A. M. Smith and S. S. Stuchly, "A solution of electromagnetic imaging using pseudo inverse transformation," IEEE Trans. Med. Imaging, vol. 3, pp. 155- 162, Dec. 1984.

[4] R. M. Lewis, "Physical optics inverse diffraction," IEEE Trans.Antennas Propagat., vol. 17, pp. 308-314, May 1969.

[5] N. N. Bojarski, "A survey of the physical optics inverse scattering identity," IEEE Trans. Antennas Propagat., vol. 30, pp. 980-989,Sept. 1982.

國際替代計量

利用基因法則及TE極化波照射重建部份掩埋完全導體之研究

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