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

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2.1 UWB Radar systems 6 2.1.2 UWB Radar Fundamentals A basic principle of the UWB radar is shown in Fig. 2.1.1. UWB radar generates and transmits short pulse through the transmit antenna TX. The signal propagates in an environment. When it meets target, the part of the electromagnetic energy is reflected from the object and propagates back to receive antenna RX. The time delay between the transmitted and received signal represents spatial distance between TX - target - RX. UWB RADAR TX RX Electromagnetic wave Target Amplitude Transmitted signal Time delay Fig. 2.1.1: Basic principle of the UWB radar. Received signal There are many advantages why to use UWB radar instead of radars with continuos waves described in [74, 109]. To name just a few most important the UWB signal can be transmitted with no carrier, the produced transmit signal requires less power, improved range measurement accuracy and object identification (greater resolution), reduced radar effects due to passive interference (rain, mist, aerosols, metalized strips, ...), and many others. 2.1.3 M-sequence UWB Radar System The UWB Maximum Length Binary Sequence (M-sequence) radar system [43, 116, 118, 111] with frequency band DC - 2.25 or 4.5 GHz is used for testing of all of the methods proposed in this work. The first idea to use a very well known M-sequence in UWB radar was proposed by Jürgen Sachs and Peter Peyerl, US patent No. 6272441 in 1996 [43]. The main advantages of using M-sequence radar instead of classical UWB radar are: the use of periodic signals avoids bias errors, it allows linear averaging for noise suppression, M-sequence has a low crest factor which allows to use limited dynamics of real systems and the signal acquisition may be carried out by undersampling. These signals of an extreme bandwidth may be sampled by using low cost, commercial Analog to Digital Converters (ADC) in combination with sampling gates. The block diagram of the used M-sequence UWB radar system is shown in Fig. 2.1.2. The N-stage shift register generates the M-sequence which is transmitted via TX. The M-sequence reflected from a target is received by RX, undersampled, time time
2.2 Through-Wall Radar Basic Model 7 System clock Signal processing Clock rate fc Binary divider N-stage shift register Σ/ADC/T&H Σ/ADC/T&H M-sequence TX Response Response RX1 RX2 Fig. 2.1.2: Block diagram of M-sequence UWB radar system. averaged, and correlated with the transmitted one. In principle, after the correlation, the output from the M-sequence radar system is the same as the output from a classic UWB pulse radar system. Therefore, the common signal processing techniques could be used after the data are gathered from radars. An analysis of 2 Dimensional (2D) target positioning accuracy for M-sequence UWB radar system under ideal conditions with the concentration on error caused by sampling with finite frequency we described in [2]. Two M-sequence UWB radars with number of chips M = 511 and clock frequency fc1 = 4.5 GHz or fc2 = 9 GHz are used for our experiment. One chip represents time interval between the two nearest impulses in M-sequence. Msequence generator has N = 7 stages. For more information about M-sequence UWB radar see [43, 116, 118]. 2.2 Through-Wall Radar Basic Model Through-wall radar (TWR) basic model specifies all processes which contribute to the measured data. These processes are caused mainly by the measurement system, the measurement environment and partly also by measured objects. For description of this model TWR system with one RX and one TX stationary antenna is used. Antenna signal effects would be shown for both, RX and TX antennas. The electric field which is generated by the TX antenna is called Erad and could be modeled by [79, 125]: E rad (r, θ, ϕ, n) = 1 2πrc hT X(θ, ϕ, n) ∗ √ Z0 √ Zc ∆VS(n) ∆n (2.2.1)
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 and 16: Chapter 1 Introduction 1.1 Motivati
Page 17 and 18: 1.3 Thesis Organization 3 In additi
Page 19: Chapter 2 State Of The Art 2.1 UWB
Page 23 and 24: 2.3 SAR Scanning 9 and shall remain
Page 25 and 26: 2.4 Calibration and Preprocessing 1
Page 27 and 28: 2.4 Calibration and Preprocessing 1
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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4.2 Measurements of the Wall Parame
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4.3 Highlighting of a Building Cont
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4.4 Measurements of the Practical S
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5.1 Conclusion and Future Work 85 5
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50 100 150 200 250 300 350 400 Z 45
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50 100 150 200 250 300 350 400 Z 45
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50 100 150 200 250 300 350 400 Z 45
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50 100 150 200 250 300 350 400 Z 45
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Z [cm] Z [cm] 50 100 150 200 250 30
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Z [cm] 50 100 150 200 250 300 b) Em
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BIBLIOGRAPHY 99 [13] T. W. Barrett,
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BIBLIOGRAPHY 101 [46] G. Derveaux,
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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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