روش هاي وارون زماني در سنجش و تصوير برداري دو بعدي مايكروويو

چكيده انگليسي :

Time Reversal Techniques in 2 D Microwave Sensing and Imaging Seyed Mojtaba Razavian Sm razavian@ec iut ac ir Date of Submission 2013 4 25 Department of Electrical and Computer Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language Farsi Supervisor Dr Reza Safian rsafian@cc iut ac ir Abstract This thesis focuses on application and development of time reversal TR based signal processing techniques using ultrawideband electromagnetic waves in microwave sensing and imaging This fundamental symmetry of physics the time reversal invariance can be exploited in the domain of wave physics in acoustics and more recently in electromagnetics leading to a huge variety of experiments and instruments both for fundamental physics and engineering applications TR techniques exploit the time reversal invariance of the wave equation to take advantage of the retransmitted time reversed fields for improved focusing and imaging This is because retransmitted signals propagate backwards through the same medium and undergo similar reflection refraction and multiple scattering that they underwent during the forward propagation resulting in focusing around initial source locations The refocusing resolution can overcome the classical diffraction limit if multiple scattering occurs in intervening media With the success of initial TR experiments in acoustics there has been a strong interest in the application of TR methods using radio frequency electromagnetic waves Thanks to development of high speed digital electronics for signal acquisition and processing many applications including subsurface sensing non destructive evaluation medical imaging etc are reported by several research groups around the globe Here our motivation is to develop TR techniques using ultrawideband electromagnetic waves for the problem of through the wall imaging We start by investigating the time reversal of electromagnetic waves theoretically This is done by using both time and frequency domain analysis An integral equation for time reversal is introduced in frequency domain The results of theoretical analysis are demonstrated through numerical experiments To take advantage of time domain representation we use the finite difference time domain FDTD method for numerical analysis For the selective focusing on different scatterers in the problem domain the multi static data matrix MDM was constructed Time reversal operator is defined with the aid of the MDM Decomposition techniques such as singular value decomposition and eigenvalue decomposition is applied on these matrices to separate the contribution of each scatterer Since knowledge about wall characteristics and the background Green s function is critical for detection and imaging of obscured targets behind walls we use this method to characterize different walls There are different methods such as DORT and MUSIC that can detect and extract information of hidden objects in medium from scattered EM fields DORT method has the possibility of focusing on desired scatterer which in MUSIC this possibility do not exist while detection and localization of objects in MUSIC method can be done more accurate than DORT method The problem of DORT and MUSIC method is using many antennas for detection and localization of hidden objects which in this thesis the Independent Component Analysis has been used as decomposition of mixture signals By this method the detection and localization of buried objects with the possibility of selection can be done by only using one transmitting antenna and an array of receiving array antenna Key Words Time reversal Microwave imaging Remote sensing Time reversal operator Radar target classification Through the wall imaging Time reversal array Singular value decomposition ICA PCA FA

رضويان، مجتبي

روش هاي وارون زماني در سنجش و تصوير برداري دو بعدي مايكروويو

سنجش از دور , عملگر وارون زماني , دسته بندي اهداف راداري , تصوير برداري از پشت ديوار , ICA , PCA