Through-Wall Imaging With UWB Radar System - KEMT FEI TUKE

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1.2 Problem Formulation 2 Fig. 1.1.2: Fireman is scanning the room on fire. building with terrorists and hostages inside for a policemen. The tactics of police raid can be build up on realtime information about ground plan of the room and positions of big objects inside. How useful for the firemen can be information about current interior state of the room before they get inside? Such hazardous environment, full of smoke with zero visibility, is very dangerous and each additional information can make the difference between life and death. Security: Investigating objects through plastic, rubber, dress or other nonmetallic materials could be highly useful as an additional tool to the existing x-ray scanners. Especially it could be used for scanning baggage at the airport, truckloads on borders, dangerous boxes, etc. 1.2 Problem Formulation The UWB radar system is used for scanning of the objects behind a wall. An electromagnetic wave is transmitted via antenna system, penetrates through the wall, it is reflected by the investigated object, penetrates again through the wall, and is received back via receiver antenna. The wall cannot be too thick, and may not be from to attenuating material in the used frequency band, to allow electromagnetic wave to travel through the wall and back. Every time the wave passes into (or from) an another material, the reflection, refraction, diffraction, and absorption on the boundaries of these materials occurs [10]. Also multiple reflections between antennas, walls, and all the objects in the scanned area arise.
1.3 Thesis Organization 3 In addition, the wave changes the velocity of its propagation depending on the material properties. As the result of all these factors, the radar receives a very complex signal, full of noise and clutters, which is very difficult to interpret. The main aim of the signal processing stages between the receiver and the radar display is to decompose the received interposed signals, use them for estimation of the scanned environment and represent this information for the end users in a human understandable and effective way. There exist no explicit method how to solve this complex problem, and that is why it represents a big challenge for researchers and engineers. One has to mention that through-wall imaging is much more problematic in comparison to detection or localization of moving objects behind the wall. Whereas, in moving objects detection background subtraction can be applied, what solves a lot of problems, this approach is not possible to apply. During imaging measurements where antenna system is moving and everything what is measured is background, and that is why it cannot be subtracted. Background subtraction eliminates influence of antennas, radar electronics, walls etc. on measured objects. Therefore, a calibration in imaging have to be done with a great precision because at the final stage it would significantly affects the results. The radar imaging is well known field for a long time, mostly used for Ground Penetrating Radar (GPR) applications [76]. However, through-wall imaging has become investigated only a few years ago [60]. The most of the published methods were tested only on simulated data, and results from practical measurements are showing poor performance for most of them. Therefore, through-wall imaging has not found many applications that could be possibly used in the practical situations yet. A lot of research in signal processing as well as in radar hardware field is still required. 1.3 Thesis Organization In Section 2, the state of the art of through-wall imaging is described. The function of an UWB radar is sketched, all the preprocessing and calibration steps required for through-wall imaging are explained, and simplified mathematical and physical ideas of most of the radar migration techniques are mentioned. In Section 3, the goals of this thesis are introduced. In Section 4, the three main contributions of this thesis are described. Efficient, precise and fast time of arrival through-wall estimation is shown in Section 4.1. Precise, easy to handle and fast measurement technique for estimation of wall parameters such as thickness, permittivity, and conductivity is introduced in Section 4.2. A method of building contours highlighting is presented in Section 4.3. Basic migration methods are compared in Section 4.4 on scenario measured with M-sequence UWB radar device. Also the imaging results of real measurements based on many practical scenarios are shown. Finally,
Page 1 and 2: TECHNICAL UNIVERSITY OF KOˇSICE Fa
Page 3 and 4: Acknowledgement I give a sincere gr
Page 5 and 6: CONTENTS v 3 Goals of Dissertation
Page 7 and 8: LIST OF FIGURES vii List of Figures
Page 9 and 10: LIST OF FIGURES ix 4.4.3 Aquarium f
Page 11 and 12: LIST OF FIGURES xi List of Symbols
Page 13 and 14: LIST OF FIGURES xiii kx - Horizonta
Page 15: Chapter 1 Introduction 1.1 Motivati
Page 19 and 20: Chapter 2 State Of The Art 2.1 UWB
Page 21 and 22: 2.2 Through-Wall Radar Basic Model
Page 23 and 24: 2.3 SAR Scanning 9 and shall remain
Page 25 and 26: 2.4 Calibration and Preprocessing 1
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Page 29 and 30: 2.5 Radar Imaging Methods Overview
Page 55 and 56: Chapter 4 Selected Research Methods
Page 57 and 58: 4.1 Through-Wall TOA Estimation 43
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4.1 Through-Wall TOA Estimation 53
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4.2 Measurements of the Wall Parame
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5.1 Conclusion and Future Work 85 5
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BIBLIOGRAPHY 99 [13] T. W. Barrett,
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BIBLIOGRAPHY 103 [81] S. Kidera, T.
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BIBLIOGRAPHY 105 [115] J. Sachs, M.
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BIBLIOGRAPHY 107 [150] O. Yilmaz, S
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Through-Wall Imaging With UWB Radar System - KEMT FEI TUKE

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