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Title: Strategies for inverse profiling of two dimensional dielectric scatterers using electromagnetic illumination
Researcher: Thomas, Vinu
Guide(s): Mathew, K T
Keywords: Electromagnetic tomography
Electromagnetic imaging
Tomographic imaging
Upload Date: 20-Apr-2012
University: Cochin University of Science and Technology
Completed Date: 09/09/2008
Abstract: Electromagnetic tomography has been applied to problems in nondestructive evolution, ground-penetrating radar, synthetic aperture radar, target identification, electrical well logging, medical imaging etc. The problem of electromagnetic tomography involves the estimation of cross sectional distribution dielectric permittivity, conductivity etc based on measurement of the scattered fields. The inverse scattering problem of electromagnetic imaging is highly non linear and ill posed, and is liable to get trapped in local minima. The iterative solution techniques employed for computing the inverse scattering problem of electromagnetic imaging are highly computation intensive. Thus the solution to electromagnetic imaging problem is beset with convergence and computational issues. The attempt of this thesis is to develop methods suitable for improving the convergence and reduce the total computations for tomographic imaging of two dimensional dielectric cylinders illuminated by TM polarized waves, where the scattering problem is defmed using scalar equations. A multi resolution frequency hopping approach was proposed as opposed to the conventional frequency hopping approach employed to image large inhomogeneous scatterers. The strategy was tested on both synthetic and experimental data and gave results that were better localized and also accelerated the iterative procedure employed for the imaging. A Degree of Symmetry formulation was introduced to locate the scatterer in the investigation domain when the scatterer cross section was circular. The investigation domain could thus be reduced which reduced the degrees of freedom of the inverse scattering process. Thus the entire measured scattered data was available for the optimization of fewer numbers of pixels. This resulted in better and more robust reconstructions of the scatterer cross sectional profile. The Degree of Symmetry formulation could also be applied to the practical problem of limited angle tomography, as in the case of a buried pipeline, where the ill posedness is much larger. The formulation was also tested using experimental data generated from an experimental setup that was designed. The experimental results confirmed the practical applicability of the formulation.
Pagination: 186p.
Appears in Departments:Department of Electronics

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01_title.pdfAttached File28.86 kBAdobe PDFView/Open
02_certificate.pdf99.22 kBAdobe PDFView/Open
03_declaration.pdf24.63 kBAdobe PDFView/Open
04_abstract.pdf59.31 kBAdobe PDFView/Open
05_table of contents.pdf46.4 kBAdobe PDFView/Open
06_acknowledgement.pdf50.28 kBAdobe PDFView/Open
07_chapter 1.pdf464 kBAdobe PDFView/Open
08_chapter 2.pdf775.7 kBAdobe PDFView/Open
09_chapter 3.pdf956.41 kBAdobe PDFView/Open
10_chapter 4.pdf1.01 MBAdobe PDFView/Open
11_chapter 5.pdf3.1 MBAdobe PDFView/Open
12_chapter 6.pdf1.51 MBAdobe PDFView/Open
13_chapter 7.pdf187.7 kBAdobe PDFView/Open
14_publications.pdf170.49 kBAdobe PDFView/Open

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