Inverse scattering problem (ISP) has been of considerable interest in remote sensing, biomedical diagnosis, military surveillance, nondestructive evaluation, oil exploration, etc. This talk presents a numerical method to solve inverse scattering problems. The recently proposed subspace-based optimization method (SOM) is found to be effective in solving ISP. The essence of the SOM is that a part of the secondary source is determined from the spectrum analysis without using any optimization, whereas the rest is determined by an optimization method. Since the optimization is carried out in a smaller dimensional space, the algorithm significantly speeds up the convergence. There is a great flexibility in partitioning the space of secondary source into two orthogonally complementary subspaces. This flexibility enables the algorithm to perform robustly against noise. On the basis of the SOM, a twofold SOM (TSOM) and its variation, the FFT-TSOM, are proposed to solve in a more stable and more efficient manner the two-dimensional (2D) and three-dimensional (3D) electromagnetic ISP. Numerical simulations validate the efficacy of the proposed method: robustness against noise, fast convergence, high resolution, and the ability to deal with scatterers of special shapes.
Dr. Chen received the B.S. and M.S. degrees in electrical engineering from Zhejiang University, China, in 1999 and 2001, respectively, and the Ph.D. degree from the Massachusetts Institute of Technology, USA, in 2005. Since then he joined the Department of Electrical and Computer Engineering, National University of Singapore, Singapore, and he is currently an Associate Professor. His research interests are mainly electromagnetic inverse problems. In particular, he is experienced in reconstructing electromagnetic parameters of obscured targets based on data of how they scatter incoming electromagnetic excitations. He has published more than 80 journal papers on inverse-scattering problems, material parameter retrieval, and optical microscopy. He visited the University of Paris-SUD 11 in May-June 2010 as an invited visiting Associate Professor. He was the recipient of the Young Scientist Award by the Union Radio-Scientifique Internationale (URSI) in 2010. He is presently taking sabbatical leave at the Stanford University, where he works on microwave impedance tomography.