M-sequenze based ultra-wideband radar and its application to crack detection in salt mines [Elektronische Ressource] / Ralf Herrmann. Gutachter: Motoyuki Sato ; Reinhard Knöchel. Betreuer: Reiner Thomä

Ralf Herrmann

Informations

• Publié par: technische_universitat_ilmenau
• Publié le: 01 janvier 2011
• Nombre de lectures: 16
• Langue: English
• Poids de l'ouvrage: 34 Mo

Extrait

IlmenauUniversityofTechnology
Department of Electrical Engineering and Information Technology
M-sequencebasedultra-widebandradarand
itsapplicationtocrackdetection
insaltmines
Dipl.-Ing. Ralf Herrmann
Dissertation zur Erlangung des akademischen Grades
Doktor-Ingenieur (Dr.-Ing.)
vorgelegt der Fakultät für Eletrotechnik und Informationstechnik der
Technischen Universität Ilmenau von Dipl.-Ing. Ralf Herrmann, geb.
am 19.09.1978 in Schmalkalden
Gutachter:
1. Prof. Dr.-Ing. habil. Reiner S. Thomä
2. Prof. Dr.-Ing. Motoyuki Sato
3. Prof. Dr.-Ing. Reinhard Knöchel
Vorgelegtam: 07.07.2011
Verteidigtam: 21.10.2011
URN: urn:nbn:de:gbv:ilm1-2011000344II
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Acknowledgement
“Zwei Dinge sollten Kinder von ihren Eltern bekommen:
1Wurzeln und Flügel . . . ” (J. W. v. Goethe, 1749 - 1832)
thEven though times are very different now than they used to be in the 18 century, some
wisdom is even more true today. Without contribution of so many people it is unthinkable
to follow an academic path and finish a dissertation.
I want to express my deep gratitude to my parents, grandparents, brother, and friends for
everlasting support and encouragement on my way.
Besides personal support, good education is invaluable to unfold one’s potential. Starting
from my teachers at school, the lecturers at the Ilmenau University of Technology during
my years of study to my colleagues at the Electronic Measurement Research Lab I like to
thank everybody for providing knowledge, scientific stimulation, and motivation.
I want to especially thank my supervisors Prof. Dr.-Ing. Habil. Reiner Thomä and Dr.-
Ing. Jürgen Sachs for giving me the chance to work on an interesting research project,
continues scientific guidance, and numerous technical discussions and support. Fur-
thermore, I want to thank Prof. Dr. Motoyuki Sato and his colleagues at the Centre for
Northeast Asian Studies from the Tohoku University in Sendai (Japan) for accepting me
as a guest student and introducing many aspects of radar data processing.
Finally, the work presented in this dissertation was supported by the German Federal
Ministry of Education and Research (BMBF) under grant number 02C1194 from the years
2004 to 2008. I also acknowledge the help of our project partners at BoRaTec GmbH
Weimar and the colleagues from Fraunhofer IZFP Dresden in geological matters and
during measurement campaigns.
Dipl.-Ing. R.Herrmann Ilmenau, July 6, 2011
1Translation — Two things children should receive from their parents: roots and wings ...
R. HerrmannIV
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Contents
Acknowledgement III
List of Figures VIII
List of Tables XI
List of Abbreviations and Symbols XII
Abstract XVII
Abstrakt XIX
1 Introduction to non-destructive testing 1
1.1 Non-destructive testing — an emerging research field with many applications . . 2
1.2 A challenging task — inspection of the disaggregation zone in salt mines . . . . 4
1.3 Properties of the disaggregation zone in salt rock and NDT sensors . . . . . . . 6
1.4 Current radar sensors in salt mines and GPR . . . . . . . . . . . . . . . . . . . 8
2 Theoretical analysis and design goals for a new sensor system 11
2.1 Propagation conditions for electromagnetic waves within salt rock . . . . . . . . 11
2.2 Bandwidth and frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2.2.1 Scattering of thin gaps or layers . . . . . . . . . . . . . . . . . . . . . . 15
2.2.2 of small volume defects . . . . . . . . . . . . . . . . . . . . 19
2.3 Mode of operation — electromagnetic wave interaction with salt rock . . . . . . 21
2.3.1 Electro-magnetic surface waves . . . . . . . . . . . . . . . . . . . . . . 22
2.3.2 Radar sensor using antennas . . . . . . . . . . . . . . . . . . . . . . . . 23
2.3.3 Antenna polarisation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
2.4 Dynamic range requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
2.4.1 Dynamic range for UWB time domain signals . . . . . . . . . . . . . . . 27
2.4.2 Setup for a typical measurement situation . . . . . . . . . . . . . . . . . 29
2.4.3 Simplified model for dynamic range simulation . . . . . . . . . . . . . . 30
2.4.4 Results of dynamic range simulation for thin gaps . . . . . . . . . . . . 32
2.5 Summary of design goals for the new UWB sensor . . . . . . . . . . . . . . . . 37
3 UWB system design for detection of sub-mm disaggregation in salt 39
3.1 Overview of available UWB electromagnetic sensor technologies . . . . . . . . . 39
3.1.1 CW/FMCW principle . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
3.1.2 Vector network analysers . . . . . . . . . . . . . . . . . . . . . . . . . . 43
3.1.3 Impulse radar. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
R. HerrmannVI Contents
3.1.4 Noise and pseudo-noise principles . . . . . . . . . . . . . . . . . . . . . 46
3.2 The starting point — review of the M-Sequence UWB sensor principle . . . . . 49
3.2.1 RF chipset of basic M-Sequence devices . . . . . . . . . . . . . . . . . . 50
3.2.2 Digital backend of basic devices . . . . . . . . . . . . . . . 54
3.3 New 12 GHz bandwidth M-Sequence UWB sensor . . . . . . . . . . . . . . . . 55
3.3.1 Extended M-Sequence stimulus . . . . . . . . . . . . . . . . . . . . . . 56
3.3.2 Software-defined dense equivalent time sampling with four receivers . . . 60
3.3.3 Frontend for measuring full two-port S-parameters and calibration . . . . 63
3.4 Summary of system design for a 12 GHz bandwidth M-Sequence sensor . . . . . 65
4 Uniform dense equivalent time sampling 67
4.1 General aspects of sampling for UWB sensors . . . . . . . . . . . . . . . . . . . 69
4.2 Analysis of accuracy requirements for uniform dense sampling . . . . . . . . . . 71
4.2.1 Periodic non-uniform sampling with sine signals . . . . . . . . . . . . . . 72
4.2.2 Periodicrm sa with an UWB stimulus . . . . . . . . . . 76
4.3 Calibration of phase states for uniform dense sampling . . . . . . . . . . . . . . 81
4.3.1 Phase shifter control hardware and timing. . . . . . . . . . . . . . . . . 81
4.3.2 Phase calibration . . . . . . . . . . . . . . . . . . . . . . 84
4.4 Summary of phase shifter control calibration for uniform dense equivalent time
sampling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
5 Device clutter removal by full 2-port calibration 95
5.1 Recapitulation of basic coaxial calibration methods . . . . . . . . . . . . . . . . 96
5.1.1 Example: 3-term calibration . . . . . . . . . . . . . . . . . . . . . . . . 98
5.2 Full two-port calibration of M-Sequence UWB-sensors with 8-term method . . . 101
5.2.1 Choice of calibration method . . . . . . . . . . . . . . . . . . . . . . . 101
5.2.2 Formulation and implementation of 8-term correction . . . . . . . . . . 105
5.2.3 Performance figures of 8-term correction . . . . . . . . . . . . . . . . . 110
5.3 Accuracy analysis of calibrated MLBS system . . . . . . . . . . . . . . . . . . . 116
5.3.1 Calibration repeatability and long-term effects . . . . . . . . . . . . . . 116
5.3.2 Comparison of calibration performance . . . . . . . . . . . . . . . . . . 123
5.4 Summary of coaxial calibration for the new M-Sequence system . . . . . . . . . 129
6 Selected salt mine measurement results 133
6.1 Measurement setup in salt mines . . . . . . . . . . . . . . . . . . . . . . . . . 133
6.1.1 Antenna type and arrangement . . . . . . . . . . . . . . . . . . . . . . 135
6.2 Data processing for detection of disaggregation zone . . . . . . . . . . . . . . . 139
6.2.1 Removal of antenna crosstalk . . . . . . . . . . . . . . . . . . . . . . . 140
6.2.2 Suppression of surface reflection . . . . . . . . . . . . . . . . . . . . . . 142
6.2.3 Visualisation of disaggregation zone . . . . . . . . . . . . . . . . . . . . 146
6.2.4 Typical data processing flow for disaggregation in salt rock . . . . . . . . 149
6.3 Measurement results for an old cylindrical tunnel . . . . . . . . . . . . . . . . . 150
6.3.1 Measurement setup for Bernburg . . . . . . . . . . . . . . . . . . . . . 151
6.3.2 Selected scans in 2D visualisation . . . . . . . . . . . . . . . . . . . . . 153
6.3.3 3D visualisation of a tunnel section . . . . . . . . . . . . . . . . . . . . 154
6.4 Measurement results for a newly cut tunnel in Borth . . . . . . . . . . . . . . . 157
R. HerrmannContents VII
6.4.1 Subsidence analysis of measurement results . . . . . . . . . . . . . . . . 158
6.4.2 Development of the disaggregation zone in a new tunnel stub . . . . . . 160
6.5 Comparison of UWB and ultrasonic sensor results . . . . . . . . . . . . . . . . 164
6.5.1 Properties of ultrasonic prototype sensor for inspection of the disaggrega-
tion zone . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164
6.5.2 Ultrasonic and radar results for a reference profile in Bernburg . . . . . . 166
6.6 Summary of real-world measurements in salt mines . . . . . . . . . . . . . . . . 167
7 Summary and outlook 171
7.1 Summary of UWB sensor development for salt rock inspection . . . . . . . . . . 171
7.2ry of salt rock disaggregation measurement results . . . . . . . . . . . . 175
7.3 Contributions to the state of the art . . . . . . . . . . . . . . . . . . . . . . . . 177
7.4 Aspects of further technical development . . . . . . . . . .