passive bistatic radar imaging of airplanes by using fm radio broadcasting signals abiven pierrick a

103 Pages·2014·4.76 MB·English

PASSIVE BISTATIC RADAR IMAGING OF
AIRPLANES BY USING FM RADIO
BROADCASTING SIGNALS
ABIVEN PIERRICK
A THESIS SUBMITTED FOR THE DEGREE OF
MASTER ENGINEERING
DEPARTMENT OF ELECTRICAL AND COMPUTER
ENGINEERING
NATIONAL UNIVERSITY OF SINGAPORE
2014
Declaration
I hereby declare that this thesis is my original urork aad it has been written by me in its
entirety. I have duly acknowledged all the sources of information which harre been used
in the thesis. This thesis has also not been submitted for any degre in any university
previously.
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Acknowledgments
This work could not have been performed without the contributions of various persons.
those persons all guided me and supported at some time along my work.
IwouldliketothankmysupervisorProfessorLimTengJoon,Professorinthedeparte-
ment of Electrical and Computer Engineering of the National University of Singapore,
for advising me all along the thesis and providing me the possibility of working on an
exiting topic. I also thank him to let me work with another research laboratory of the
Nanyang Technological University.
I also wish to thank Doctor Jonathan Pisane, research scientist at the Temasek Lab-
oratory of Nanyiang Technological University, for the technical discussions that we had
during the last 10 months of my thesis and for his comments that helped me to write
this thesis. I also wish to thank Doctor Danny Tan Kai Pin for his invaluable help for
the experiments that could not have been without him.
IalsowishtothankDoctorFr´ed´ericBriguiandDoctorMehdiAirighilfortheinformal
discussion on their respective field of expertise which provides me a better understanding
on passive radar technologies.
I wish to thank all my family and friends that supported me during the thesis. Espe-
cially, I would like to thank my friends who convinced me to join the NUS running team
and allowed me to meet a large number of amazing persons.
Finally, I wish to thank all the persons I forgot to mention here.
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Summary
A conventional Airport Surveillance Radar (ASR) system must transmit a signal in order
to detect approaching aircraft, and thus a frequency band has to be allocated to the ASR
system. Passive bistatic radar (PBR) systems, on the other hand, reuse electromagnetic
signals already present in order to detect, localize and identify an object within a given
area. PBR is a well-known topic but prior research has mainly focused on detection and
estimation, and relatively little work has been done on PBR imaging. The use of the FM
band for that purpose is motivated by the geographic prevalence of radio broadcasting
and the large size of an FM cell, and is the subject of this thesis.
Firstly, the tomography principles applied to radar imaging are presented for the
monostaticconfigurationandthengeneralizedtothebistaticconfiguration. Secondly, the
feasibility of using FM radio broadcasting signals is studied for imaging airborne aircraft
using a realistic configuration and a validation of the theoretical work is done using a
bright point model. The feasibility of the PBR imaging is considered for the Singaporean
configuration which has two transmitters, one in Johor Bahru (Malaysia) and the other
in Bukit Timah(Singapore). Thirdly, a second validation of the theory is undertaken by
developinganewtoolforsimulatingtheelectromagneticfieldreflectedoffanobjectbased
on the NEC2 program. It is based on the transformation of a CAD model given by free
license software to an interpretable model for NEC2 that composes of wire coordinates
only. PBR images are built from the simulated RCS obtained. Finally an experimental
data collection campaign has been executed to compare the theory and the simulation
with the reality in the Singapore vicinity by using the FM radio broadcasting signal
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transmitted from Bukit Batok (Singapore) and airplanes approaching Changi Airport.
A PBR system has been built and is able to track and detect targets but the too low
power of the reflected signals prevents us from extracting the RCS of the targets and
from generating their PBR images.
The main contribution is the successful construction of interpretable PBR images
givenarealisticconfigurationandlimitedtrajectoriesfortheairplanesbasedonsimulated
data. It also provides a new tool for obtaining an estimation of the RCS of an airplane
at a low frequency for a limited cost. Moreover, a PBR system has been built and was
able to detect and to track real targets landing and taking off at Changi airport. Finally,
all the work was derived for a special configuration but the methodology can be easily
applied in other configurations.
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Contents
Acronyms xi
1 Introduction 1
1.1 Targets Considered . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 Radar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2.1 Monostatic Radar Description . . . . . . . . . . . . . . . . . . . . 2
1.2.2 Bistatic Radar Description . . . . . . . . . . . . . . . . . . . . . . 3
1.2.3 Passive Radar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.2.4 Radar Imaging . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.3 Notation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.4 Contribution Of The Thesis . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.5 Organisation Of The Thesis . . . . . . . . . . . . . . . . . . . . . . . . . 7
2 Principles Of Passive Bistatic Radar Imaging 8
2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.2 Radar Cross-Section And Radar Image Definition . . . . . . . . . . . . . 9
2.2.1 Electrical Field Modeling . . . . . . . . . . . . . . . . . . . . . . . 9
2.2.2 Polarization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
2.2.3 Radar Cross Section . . . . . . . . . . . . . . . . . . . . . . . . . 11
2.2.4 Radar Image . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
2.3 A Tomography Approach To Bistatic Radar Imaging . . . . . . . . . . . 14
2.3.1 Radon Transform And Projection Slice Theorem . . . . . . . . . . 14
2.3.2 Tomography Principles Applied To Monostatic Radar imaging . . 16
2.3.3 Tomography Principles Applied To Bistatic Radar Imaging . . . . 22
2.4 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
3 Characteristic Of The Singaporean Configuration 26
3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
3.2 Practical PBR imaging . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
3.2.1 Block Diagram Of The PBR System Considered . . . . . . . . . . 27
3.2.2 PBR imaging implementation . . . . . . . . . . . . . . . . . . . . 28
3.2.3 Resolution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
3.3 Actual Configuration Constraints . . . . . . . . . . . . . . . . . . . . . . 30
3.3.1 General Presentation Of The Bistatic Configuration . . . . . . . . 30
3.3.2 Transmitters Constraints . . . . . . . . . . . . . . . . . . . . . . . 31
3.3.3 Airplanes Trajectory Constraints . . . . . . . . . . . . . . . . . . 34
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3.3.4 Consequence On The Fourier Space Coverage . . . . . . . . . . . 35
3.4 Example Of Radar Images Generated By Using Bright Point Model And
Actual Airplane Trajectory . . . . . . . . . . . . . . . . . . . . . . . . . . 37
3.4.1 Bright-Point Model . . . . . . . . . . . . . . . . . . . . . . . . . . 37
3.4.2 Passive Bistatic Radar Images . . . . . . . . . . . . . . . . . . . . 38
3.5 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
4 Simulated Electromagnetic Airplane Model 41
4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
4.2 General Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
4.3 Electromagnetic Model And Simulation . . . . . . . . . . . . . . . . . . . 43
4.3.1 The Importance Of A Conformal Mesh . . . . . . . . . . . . . . . 43
4.3.2 Maxwell’s Equation . . . . . . . . . . . . . . . . . . . . . . . . . . 44
4.3.3 E-Field Reflected Off A Sphere And The Electromagnetic Regions 46
4.3.4 Electromagnetic Simulation . . . . . . . . . . . . . . . . . . . . . 47
4.3.5 The Methods Of Moments (MoM) . . . . . . . . . . . . . . . . . . 48
4.3.6 The NEC2 Software . . . . . . . . . . . . . . . . . . . . . . . . . 48
4.3.7 Constraints Of NEC2 . . . . . . . . . . . . . . . . . . . . . . . . . 49
4.4 From CAD Model To NEC2 Interpretable Model . . . . . . . . . . . . . . 51
4.5 Validation Of The Approach And Limitations . . . . . . . . . . . . . . . 57
4.5.1 Verification On A Sphere . . . . . . . . . . . . . . . . . . . . . . . 57
4.5.2 Estimation Of The Computation Time And Memory Required . . 58
4.5.3 Remaining Limitations . . . . . . . . . . . . . . . . . . . . . . . . 60
4.6 Simulation Of Radar Cross Section Of Airplanes . . . . . . . . . . . . . . 61
4.6.1 RCS At Different Frequencies . . . . . . . . . . . . . . . . . . . . 61
4.6.2 Variation Of RCS In Function Of An Orientation Error Of The
Airplanes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
4.7 Simulation Of PBR Images Using Low Frequency Signals . . . . . . . . . 64
4.7.1 Simulation Of Passive Bistatic Radar Image . . . . . . . . . . . . 64
4.7.2 SimulationOfPassivebistaticRadarImageUsingActualAirplanes
Trajectory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
4.8 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
5 Passive Bistatic Radar Using Real Data 69
5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
5.2 Design Of The Experiment . . . . . . . . . . . . . . . . . . . . . . . . . . 70
5.2.1 General Description Of The Real Data Collection And Processing 70
5.2.2 Acquisition Of Measured And Reference Signals . . . . . . . . . . 71
5.2.3 Generation Of RD Map And Extraction Of RCS . . . . . . . . . . 72
5.2.4 Synchronization And Filtering Of The ADSB Data . . . . . . . . 74
5.3 Experimental Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
5.3.1 Range Doppler Map Obtained . . . . . . . . . . . . . . . . . . . . 76
5.3.2 RCS Extraction Of Commercial Airliner By Using Real Data . . . 77
5.3.3 Discussion On The Passive Bistatic Radar System Built . . . . . . 81
5.4 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
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6 Conclusion 83
6.1 Summary Of The Thesis . . . . . . . . . . . . . . . . . . . . . . . . . . . 83
6.2 Future Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
6.2.1 Overcoming NEC2 limitations . . . . . . . . . . . . . . . . . . . . 85
6.2.2 Improving the extraction of the CRCS from real data measurements 86
6.2.3 Use of multiple FM station transmitters and receivers . . . . . . . 86
6.2.4 Considering another signal . . . . . . . . . . . . . . . . . . . . . . 86
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List of Tables
3.1 Parameters used for the bistatic radar . . . . . . . . . . . . . . . . . . . . 32
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List of Figures
1.1 A general description of a radar system . . . . . . . . . . . . . . . . . . . 2
1.2 The bistatic configuration. . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.3 Block diagram of radar imaging processing developed in this thesis. . . . 5
2.1 Block diagram of radar imaging processing and focus on this Chapter. . . 9
2.2 Description of the polarization . . . . . . . . . . . . . . . . . . . . . . . . 12
2.3 A monostatic configuration. . . . . . . . . . . . . . . . . . . . . . . . . . 17
2.4 A bistatic configuration. . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
3.1 Block diagram of the simulated PBR imaging system. . . . . . . . . . . . 27
3.2 GeometricconfigurationusedfortheISARimagingusingapassivebistatic
radar. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
3.3 Difference between the Mean Bandwidth (MBW) and the Full Width at
Half Maximum (FWHM). Reproduced from [1]. . . . . . . . . . . . . . . . 29
3.4 SingaporeanconfigurationconsideredfortheISARimagingusingapassive
bistatic radar. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
3.5 Presentation of the parameters used in the power link budget equation [2]. 32
3.6 Representation of the frequency, expressed in MHz, repartition available
from the two transmitters considered. . . . . . . . . . . . . . . . . . . . . 33
3.7 Trajectories of commercial airliners in the Cartesian representation. . . . 34
3.8 Trajectory represented in the (α,β)-representation. . . . . . . . . . . . . 35
3.9 Covered Fourier domain with those transmitters by five targets. . . . . . 36
3.10 Covered Fourier domain with those transmitters by only one target. . . . 37
3.11 Bright point model descritpion. . . . . . . . . . . . . . . . . . . . . . . . 38
3.12 PBR images of 5 bright points using a real trajectory. . . . . . . . . . . . 39
3.13 PBR image of 9 bright points using a real trajectory. . . . . . . . . . . . 39
4.1 Block diagram of the radar imaging processing. . . . . . . . . . . . . . . 43
4.2 CAD model and conformal wire model of a F16 fighter airplane. . . . . . 44
4.3 Radar cross section of metal sphere from Mie’s theory. . . . . . . . . . . 47
4.4 BlockdiagramoftheprocessingforobtainingaNEC2cinterpretablemodel
from a CAD model. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
4.5 Example of a face divided in four sub-faces and the wires model derivated
from it. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
4.6 Example of a face crossed by a wire and the modification of the wires
structure induced . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
4.7 RCS of a 10-m sphere with 5376 faces. . . . . . . . . . . . . . . . . . . . 57
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