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

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4.2 Measurements of the Wall Parameters by Reflectometry 62 Propagation time [ns] 17.7 22.2 26.6 31.1 35.5 40.0 44.4 48.8 Wall-Air interface Next wall out of interest Air-Wall interface 50 100 150 200 250 300 350 400 Propagation time [ns] 4.4 8.8 13.3 17.7 22.2 26.6 Next wall out of interest Wall-Air interface Air-Wall interface Clutters 50 100 150 200 250 Number of impulse responses Number of impulse responses a) Measured data without crosstalk b) After synchronization and normalization Fig. 4.2.4: B-scans, antennas were moved from 0.5 m to 1.5 m from the wall. a) Measured data, oversampled and without crosstalk. b) After synchronization and normalization, next wall is 1.8 m from measured wall. 4.2.4 Algorithm Description As mentioned above, the first step is to determine the reflection coefficient Γ of the outer surface in order to be able to determine the wall permittivity. Since the incident wave is not known in practice, a reference measurement hm(n) was made beforehand and stored in the device memory. For that purpose, we used a large sheet of metal Γ = −1 and measured the reflection at 1 m distance. Since we have supposed wall parameters as frequency independent, we are able to determine Γ of the first surface from the peak values of the measured data: Γ = − �h1(n)� ∞ �hm(n)� ∞ = − �h(n)�∞ . (4.2.5) �hm(n)�∞ The reflection coefficient of a wall is always negative (compare (4.2.1) and see Fig. 4.2.5). The infinity norm is a positive number, hence the minus in (4.2.5). The determination of h(n) has to be done carefully by using the same wall distance for synchronization as in the hm(n) measurement in order to respect the spreading loss of the waves. However, a distance measurement to the wall is not required, it can be easily obtained from position of h1(n). Now, we can calculate the wall permittivity: εrw = (1 − Γ)2 (1 + Γ) 2 (4.2.6)
4.2 Measurements of the Wall Parameters by Reflectometry 63 a) b) Normalized Amplitude Normalized Amplitude 0.8 0.6 0.4 0.2 0 -0.2 -0.4 -0.6 -0.8 -1 0 2.2 4.4 6.6 8.8 11.1 13.3 15.5 17.8 20.0 22.2 24.4 0.8 0.6 0.4 0.2 0 -0.2 -0.4 -0.6 -0.8 Reflections from both interfaces - h(n) Air-Wall interface h 1(n) �t Wall-Air interface h 2(n) Next wall out of interest Second reflection - after removing first reflection Wall-Air interface h 2(n) Next wall out of interest Time [ns] -1 0 2.2 4.4 6.6 8.8 11.1 13.3 15.5 17.8 20.0 22.2 24.4 Time [ns] Fig. 4.2.5: Mean of reflections from wall interfaces. a) Reflection from both interfaces. b) Reflection from wall-air interface, after removing the first reflection. and the propagation speed within the wall: vw = c √ . (4.2.7) εrw The propagation time ∆t (see Fig. 4.2.5) within the wall will give the wall thickness: Dw = vw∆t . (4.2.8) 2 Time ∆t results from the time position of the maximum of h2(n) referred to the first reflection. However, the h1(n) and h2(n) may overlap each other as it is shown in Fig. 4.2.6. It is mostly obvious when the wall is too thin. In this case a wall thickness is only 13 cm. Therefore, we firstly subtract the first reflection h1(n) from the data in order to gain the improved reflection from the inner surface. Since the wall parameters are frequency independent, we can suppose that h1(n)
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TECHNICAL UNIVERSITY OF KOˇSICE Fa
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Acknowledgement I give a sincere gr
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CONTENTS v 3 Goals of Dissertation
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LIST OF FIGURES vii List of Figures
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LIST OF FIGURES ix 4.4.3 Aquarium f
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LIST OF FIGURES xi List of Symbols
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LIST OF FIGURES xiii kx - Horizonta
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Chapter 1 Introduction 1.1 Motivati
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1.3 Thesis Organization 3 In additi
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Chapter 2 State Of The Art 2.1 UWB
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2.2 Through-Wall Radar Basic Model
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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
Page 71 and 72: 4.2 Measurements of the Wall Parame
Page 75: 4.2 Measurements of the Wall Parame
Page 81 and 82: 4.3 Highlighting of a Building Cont
Page 91 and 92: 4.4 Measurements of the Practical S
Page 99 and 100: 5.1 Conclusion and Future Work 85 5
Page 101 and 102: 50 100 150 200 250 300 350 400 Z 45
Page 103 and 104: 50 100 150 200 250 300 350 400 Z 45
Page 105 and 106: 50 100 150 200 250 300 350 400 Z 45
Page 107 and 108: 50 100 150 200 250 300 350 400 Z 45
Page 109 and 110: Z [cm] Z [cm] 50 100 150 200 250 30
Page 111 and 112: Z [cm] 50 100 150 200 250 300 b) Em
Page 113 and 114: BIBLIOGRAPHY 99 [13] T. W. Barrett,
Page 115 and 116: BIBLIOGRAPHY 101 [46] G. Derveaux,
Page 117 and 118: BIBLIOGRAPHY 103 [81] S. Kidera, T.
Page 119 and 120: BIBLIOGRAPHY 105 [115] J. Sachs, M.
Page 121: BIBLIOGRAPHY 107 [150] O. Yilmaz, S
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Through-Wall Imaging With UWB Radar System - KEMT FEI TUKE

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