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چكيده انگليسي :

Microwave Imaging of Two Dimensional Objects Exploiting Level Set Method Mohammad Reza Eskandari Mr eskandari@ec iut ac ir Date of Submission 2010 04 15 Department of Electrical and Computer Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language Farsi Supervisors Reza Safian rsafian@cc iut ac ir Abolghasem Zeidaabadi Nezhad zeidabad@cc iut ac ir Abstract Electromagnetic inverse scattering problems have so many applications in engineering and science that we may say they have the same importance as the direct electromagnetic problems The goal is to identify different characteristics of an object such as physical shape and permittivity exploiting the scattered fields The main two categories of applications of inverse electromagnetic problems are nondestructive testing and remote detection Medical imaging ground penetrating radars security detections which are used in geophysics medical centers and mines are examples of these applications Inverse scattering problems can be solved in time or frequency domain Since calculation and measurement of the scattered fields in frequency domain are easier solution of the inverse scattering problems in the frequency domain is more common In general these problems are not well posed and they are usually nonlinear This makes them much more complex with respect to the direct problems which are usually linear and well posed This complexity is much more severe when the wavelength of the incident wave is comparable with the size of the scatterer The inverse scattering methods are qualitative or quantitative The quantitative methods are generally slower but more accurate compared to the qualitative methods In this thesis we are concerned about the microwave imaging approach Conceptually it is an electromagnetic inverse scattering problem where the goal is to characterize unknown objects from measurements of the scattered fields that result from their interaction with a known incident wave in the microwave frequency range The majority of the electromagnetic EM spectrum can be used for imaging with different operating frequencies providing different information about the object being imaged Promising results concerning the use of microwave imaging for early detection of breast cancer have been reported recently in the literature where the potential for resolving small tumors has been demonstrated In security applications scanning and surveillance of people cannot use ionizing radiation for safety reasons The current metal detection solution is limited as it cannot see underneath clothing Less intrusive microwave imaging has obvious advantages in being more reliable covert and less disruptive to passengers checkpoints Shape reconstruction of two dimensional perfect electric conductors is a basic inverse electromagnetic problem which its solution methods can be expanded to more complex problems In this thesis shape reconstruction of two dimensional perfect electric conductor objects in free space or in presence of the ground plane is discussed Level set method which is an iterative method is used for shape optimization The incident waves are considered to be transverse magnetic TM This is a quantitative method which is generally slow Using conjugate gradient fast marching and frequency hopping techniques accelerates the method and reduces the effect of measurement noise Keywords Inverse Scattering Ill Posed Problems Level Set Method conjugate gradient Method

اسكندري، محمدرضا

تصوير برداري مايكروويو از پراكنده ساز دو بعدي با استفاده از روش مجموعه تراز

پراكندگي معكوس , مسائل بدخيم , روش مجموعه تراز , روش گراديان مزدوج