穿牆多導體之頻域微波成像

Microwave Imaging in Frequency Domain for Through-Wall Multiple Conductors

沈思齊(Szu-Chi Shen)

指導教授 ： 丘建青

淡江大學/工學院/電機工程學系碩士班/碩士(2013年)

https://doi.org/10.6846/TKU.2013.00105

摘要

本論文研究穿牆多導體影像問題，利用非同步粒子群聚法(Asynchronous Particle Swarm Optimization)來處理埋藏於牆壁之後的電磁成像問題。
將未知形狀的物體，埋藏在牆壁之後，從外部入射電磁波照射埋藏在牆壁之後的未知物體，並在牆壁外部量測其散射場，利用在導體表面的邊界條件及量測到的散射電場，可推導出一組非線性積分方程，將散射場積分方程式透過動差法求得散射電場相關資訊。在此使用傅立葉級數展開及描述物體的形狀，將電磁成像問題轉化為求解最佳化問題，並在演算法中使用非同步粒子群聚法重建埋藏於牆後之雙導體之形狀。藉由將量測而得的散射場和非同步粒子群聚法所計算出的散射場數值相比較，若兩個散射場之差值越小，則表示重建出來的未知物體越良好。
不論初始的猜測值如何，非同步粒子群聚法總會收斂到全域極值(Global Extreme)，因此，在數值模擬顯示中，即使最初的猜測值與實際值相差甚遠，我們仍然可求得準確的數值解，成功的重建出物體形狀函數，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。

關鍵字

逆散射 ； 電磁成像 ； 粒子群聚法 ； 穿牆成像

並列摘要

This paper presents an inverse scattering problem for the through-wall imaging problem. Two separate perfect-conducting cylinders of unknown shapes are hidden behind a homogeneous building wall and illuminated by the transverse magnetic(TM) plane wave.
After an integral formulation, a discretization using the method of moment (MoM) is applied. The through-wall imaging (TWI) problem is recast as a nonlinear optimization problem with an objective function defined by the norm of a difference between the measured and calculated scattered electric field. Thus, the shape of metallic cylinder can be obtained by minimizing the objective function.
The Asynchronous particle swarm optimization is employed to find out the global extreme solution of the object function. Numerical results demonstrate even when the initial guesses are far away from the exact shapes, and then the multiple scattered fields between two conductors are serious the good reconstruction can be obtained.
In addition, the effect of Gaussian noise on the reconstruction result is investigated and through the numerical simulation shows that we can still get good results of reconstructions.

並列關鍵字

Inverse problem ； Through-Wall Imaging ； Asynchronous Particle Swarm Optimization ； Multiple scattered

參考文獻

[1] E. Wolf, “Three-dimensional structure determination of semi-transparentobjects from holographic data,” Opt. Commun., Vol. 1, pp.153–164, Sep.-Oct. 1969.

[2] O. Mudanyalı, S. Yıldız, O. Semerci, A. Yapar and I. Akduman, “A Microwave Tomographic Approach for Nondestructive Testing of Dielectric Coated Metallic Surfaces”, IEEE Geoscience and Remote Sensing Letters, Vol. 5, No. 2, pp. 180 - 184, Apr. 2008.

[3] S. Genovesi, E. Salerno, A. Monorchio and G. Manara, “Permittivity range profile reconstruction of multilayered structures from microwave backscattering data by using particle swarm optimization,” Microwave and Optical Technology Letters, Vol. 51, No. 10, pp. 2390 - 2394, Oct. 2009.

[4] O. M. Bucci and T. Isernia, “Electromagnetic inverse scattering: Retrievable information and measurement strategies,” Radio Sci., Vol. 32, pp. 2123–2138, Nov.–Dec. 1997.

[7] A. Baussard, “Inversion of multi-frequency experimental data using an adaptive multiscale approach,” Inverse Problems, Vol. 21, pp. S15–S31, Dec. 2005.