Short-Range Ultra-Wideband Imaging with Multiple-Input Multiple-Output Arrays

227 Pages·2010·10.32 MB·English

Short-Range Ultra-Wideband Imaging
with Multiple-Input Multiple-Output Arrays
The pictures on the cover are the experiment setup of MIMO-SAR based UWB
imaging system and the resulting 3-D image of the mannequin. (See also figure
5.2 and figure 5.6 of this thesis)
Short-Range Ultra-Wideband Imaging
with Multiple-Input Multiple-Output Arrays

Proefschrift

ter verkrijging van de graad van doctor
aan de Technische Universiteit Delft,
op gezag van de Rector Magnificus prof. ir. K. C. A. M. Luyben,
voorzitter van het College voor Promoties,
in het openbaar te verdedigen op maandag 8 november 2010 om 10:00 uur

door

Xiaodong ZHUGE

elektrotechnisch ingenieur
geboren te Beijing, China
Dit proefschrift is goedgekeurd door de promotor:

Prof. DSc. O. G. Yarovyi

Samenstelling promotiecommissie:

Rector Magnificus voorzitter
Prof. DSc. O. G. Yarovyi Technische Universiteit Delft, promotor
Prof. dr. ir. L. P. Ligthart Technische Universiteit Delft
Prof. ir. P. Hoogeboom Technische Universiteit Delft
Prof. ir. F. le Chevalier Technische Universiteit Delft
Prof. dr. C. Pichot Université de Nice-Sophia Antipolis
Prof. dr.-ing. habil. R. S. Thomä Technische Universität Ilmenau

This research was partly supported by PASR project PROBANT (Grant
Agreement no. SEC5-PR-104000), by FP6 project Radiotect (COOP-CT-
2006-032744), and by FP7 project ATOM (FP7-AAT-2008-RTD-1-234014)

ISBN/EAN 978-94-6113-026-6
Short-Range Ultra-Wideband Imaging with Multiple-Input Multiple-Output
Arrays.
Dissertation at Delft University of Technology.
Copyright © 2010 by Xiaodong Zhuge.

All rights reserved. No parts of this publication may be reproduced or
transmitted in any form or by any means, electronic or mechanical, including
photocopy, recording, or any information storage and retrieval system,
without permission in writing from the author.
To my family

CONTENTS vii

Contents

1 Introduction 1
1.1 Overview of array-based UWB imaging systems...................................3
1.2 State-of-the-art in microwave imaging....................................................5
1.3 Research objectives.................................................................................9
1.4 Challenges and chosen approach...........................................................10
1.5 Novelties and main results.....................................................................12
1.6 Research framework..............................................................................15
1.7 Outline of the thesis...............................................................................16
References........................................................................................................19

2 Ultra-wideband focusing 25
2.1 Review of existing theories.................................................................26
2.2 Formulation of electromagnetic focused beam...................................27
2.2.1 Ultra-wideband electromagnetic missile................................27
2.2.2 Imaging with synthetic aperture radar....................................31
2.3 Interference region in the near-field and beyond................................35
2.4 Spatial sampling criteria.....................................................................38
2.5 Sidelobe level of UWB aperture.........................................................40
2.6 Resolution and beam pattern...............................................................42
2.7 Characteristics of sparse aperture array..............................................44
2.7.1 Effect of center frequency......................................................45
2.7.2 Effect of fractional bandwidth...............................................46
2.7.3 Effect of aperture size............................................................47
2.7.4 Effect of number of elements within the aperture..................48
2.8 Summary.............................................................................................49
References........................................................................................................50
viii CONTENTS
3 Multiple-input multiple-output arrays for real-aperture imaging 51
3.1 Review of existing theories.................................................................52
3.2 Near-field wideband beam pattern formulation..................................53
3.3 Unified theory with narrowband far-field beam pattern.....................57
3.4 Effective aperture and synthetic aperture............................................61
3.5 Factorization approach........................................................................63
3.6 Design procedure................................................................................65
3.7 Near-field and bandwidth effects........................................................70
3.8 Experimental results............................................................................72
3.9 Summary.............................................................................................76
References........................................................................................................78

4 Two-dimensional planar MIMO arrays 81
4.1 Review of existing theories.................................................................82
4.2 Array redundancy and element shadowing.........................................83
4.3 Two-dimensional design methodologies............................................87
4.3.1 Equivalent uniform rectilinear array......................................87
4.3.2 Curvilinear composed array...................................................91
4.3.3 Mills Cross array....................................................................93
4.4 Experimental verification....................................................................95
4.4.1 Tx/Rx coupling within 2-D MIMO array...............................97
4.4.2 Beam pattern..........................................................................98
4.4.3 3-D volumetric imaging of distributed target.......................102
4.5 Summary...........................................................................................104
References......................................................................................................104

5 Comparison between real-aperture array and synthetic aperture 107
5.1 Theoretical comparison.....................................................................108
5.2 Experimental comparison.................................................................111
5.3 Summary...........................................................................................117
References......................................................................................................117

6 Advanced imaging algorithms for UWB MIMO array 119
6.1 Modified Kirchhoff migration..........................................................120
6.1.1 Formulation..........................................................................121
6.1.1.1 Formulation for MIMO array.......................................123
6.1.1.2 Compensation of limited aperture effects....................125
CONTENTS ix
6.1.1.3 Extending Kirchhoff integral to subsurface.................127
6.1.1.4 Efficient calculation of travel time...............................129
6.1.2 Results in free-space............................................................131
6.1.3 Results in subsurface............................................................135
6.2 MIMO range migration.....................................................................140
6.2.1 Range migration for SAR configuration..............................141
6.2.2 Formulation for MIMO array...............................................142
6.2.3 Algorithm implementation...................................................145
6.2.4 Sampling constrains.............................................................147
6.2.5 Imaging results.....................................................................149
6.3 Summary...........................................................................................154
References......................................................................................................154

7 Utilization in different applications 159
7.1 Concealed weapon detection.............................................................160
7.1.1 Prototype of the system........................................................161
7.1.2 Test results...........................................................................164
7.2 Through-wall radar...........................................................................167
7.2.1 Propagation loss...................................................................167
7.2.2 Dynamic range.....................................................................170
7.2.3 Choice of UWB technologies...............................................172
7.2.4 Prototype of through-wall imaging radar.............................173
7.2.5 Test results...........................................................................175
7.3 Ground penetrating radar in a multi-sensor fusion system...............177
7.3.1 Array-based UWB GPR Sensor...........................................178
7.3.2 GRP embedding in multi-sensor suit...................................179
7.3.3 Test results...........................................................................182
7.4 Summary...........................................................................................184
References......................................................................................................184

8 Conclusions 187
8.1 Results and novelties of this research...............................................188
8.2 Recommendations.............................................................................189

A Design of low profile UWB antenna for near-field imaging 191
A.1 Introduction.......................................................................................191
x CONTENTS
A.2 Antenna element design....................................................................193
A.3 Performances of the antenna.............................................................196
A.4 Summary...........................................................................................199
References......................................................................................................199

List of acronyms 201

Summary 203

Samenvatting 207

Author’s publications 211

Acknowledgements 215

About the author 217