Performance factors for airborne short-dwell squinted radar sensors

253 Pages·2011·9.15 MB·English

Performance factors for airborne

short-dwell squinted radar sensors

By:

Gavin Beard

A thesis presented to the University of London for the degree of Doctor of
Engineering.

Communications Engineering Doctorate Centre
Department of Electronic and Electrical Engineering
University College London

September 2010
Abstract
Millimetre-wave radar in a missile seeker for the engagement of ground targets
allows all-weather, day and night, surface imaging and has the ability to detect,
classify and geolocate objects at long ranges. The use of a seeker allows intelligent
target selection and removes inaccuracies in the target position. The selection of
the correct target against a cluttered background in radar imagery is a challenging
problem, which is further constrained by the seeker’s hardware and flight-path.

This thesis examines how to make better use of the components of radar imagery
that support target selection.

Image formation for a squinted radar seeker is described, followed by an approach
to automatic target recognition. Size and shape information is considered using a
model-matching approach that is not reliant on extensive databases of templates,
but a limited set of shape-only templates to reject clutter objects. The effects of
radar sensitivity on size measurements are then explored to understand seeker
operation in poor weather.
Size measures cannot easily be used for moving targets, where the target signature
is distorted and displaced. The ability to detect, segment and measure vehicle
dimensions and velocity from the shadows of moving targets is tested using real
and simulated data.
The choice of polarisation can affect the quality of measurements and the ability to
reject clutter. Data from three different radars is examined to help to understand the
performance using linear and circular polarisations.
For sensors operating at shorter ranges, the application of elevation monopulse to
include target height as a discriminant is tested, showing good potential on
simulated data.
The combination of these studies offers an insight into the performance factors that
influence the design and processing of a radar seeker. The use of shadow imagery
on short-dwell radar seeker imagery is an area offering particular promise.

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Declaration
I, Gavin Spencer Beard, confirm that the work presented in this thesis is my own.
Where information has been derived from other sources, I confirm that this has
been indicated in the thesis.
Signed:
Date:

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Acknowledgements
I would like to thank many of my colleagues for their assistance when I was
undertaking the projects that formed this thesis, and during the process of
completion under pressing timescales.
Thanks go to Dr Adrian Britton for providing guidance, useful suggestions, and
asking many awkward, but valuable, questions. I would also like to thank Dr
Jonathan Collier for his support in the final stages of this work and Patrick Beasley,
who has provided information and answers to my questions on radar hardware. I
would like to thank John Whitehead and Robert Gibson for their advice, feedback
and contrasting review styles. Many thanks to Andrew May, now of Dstl, for
answering questions over the years, and for many interesting discussions.
I would like to thank Professor Chris Baker, now of the Australian National
University, for accepting me as an EngD student, and I am indebted to Professor
Hugh Griffiths of UCL, who accepted me as a student at a late stage in my EngD,
and has provided much encouragement and support.
I would like to thank the MoD for funding this work and allowing publication, as well
as the Engineering and Physical Sciences Research Council (EPSRC) for
sponsorship.
Finally, thanks must go to Naomi for putting up with my work, and to my parents for
their support and for never forgetting to ask when this would be complete.

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List of contents
1 Introduction 21
1.1 Missile Sensors 21
1.2 Millimetre Wave (MMW) radar for missile seekers 23
1.3 MMW Doppler Beam Sharpening (DBS) and SAR 24
1.4 Analysis of imagery and Automatic Target Recognition 24
1.5 Motivation 25
1.6 Objectives 25
1.7 Methodology 25
1.8 Novel aspects of the work 27
1.9 Publications 27
2 Research context 28
2.1 Early History 28
2.2 2D imaging radar 29
2.3 Radar ATR 30
2.4 Factors influencing ATR performance 31
2.4.1 Amplitude 32
2.4.2 Polarisation 34
2.4.3 Use of target measurements in a seeker system 35
2.5 Summary 36
3 MMW SAR image formation and analysis 37
3.1 Introduction 37
3.2 Radar sensitivity 37
3.3 Range resolution 41
3.4 Cross-range resolution 42
3.5 Scanning effects 44
3.6 Antenna beam shape effects 49
3.7 Validation with real data 50
3.8 Image resolution conclusions 52
4 Experimental data gathering and radar simulation 53
4.1 Introduction 53
4.2 Data gathering trials – Air carry 53
4.3 Data gathering trials – Turntable 58
4.4 Radar Simulation 59
4.4.1 Introduction 59
4.4.2 Modelling validation 60
4.5 Conclusions 65
5 Object signal and shape information 66
5.1 MMW ATR Theory and Outline 66
5.1.1 ATR Summary 73
5.2 Challenges in measuring target size and shape 74
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5.3 Simple CAD model signature prediction 75
5.3.1 Introduction 75
5.3.2 Trials data 76
5.3.3 Synthetic CLTG data 77
5.3.4 CLTG models 79
5.3.5 CLTG comparison with real imagery 81
5.3.6 Snake segmentation 83
5.3.7 Model matching technique 83
5.3.8 Amplitude model matching 85
5.3.9 Application to MRMS data 86
5.3.10 Clutter rejection 88
5.3.11 Model matching summary 90
5.4 Performance effects of radar sensitivity / attenuation 91
5.4.1 Seeker sensitivity 91
5.4.2 Rain clutter backscatter 91
5.4.3 Atmospheric attenuation 94
5.4.4 Sensitivity effects in imagery 96
5.4.5 Modelling reduced sensitivity 97
5.4.6 Sensitivity effects on acquisition performance 98
5.5 Attribute measurement capability 99
5.6 Seeker Sensitivity Conclusions 108
6 Object Shadow Information 109
6.1 Introduction 109
6.2 Shadow segmentation and measurement 110
6.2.1 Shadow analysis process 111
6.2.2 Shadow search 112
6.2.3 Shadow segmentation - Adaptive contour 114
6.2.4 Shadow segmentation – Model based 115
6.2.5 Coordinate transformation 117
6.2.6 Shadow analysis 118
6.3 Software implementation 120
6.4 Data analysis and results 122
6.4.1 Air carry trials data 122
6.4.2 Data available 124
6.4.3 Analysis of air-carry imagery 127
6.4.4 Aspect angle considerations 131
6.4.5 CLTG Data 132
6.5 CLTG shadow velocity estimation 135
6.5.1 Velocity measurement using bright target signature 135
6.5.2 Velocity measurement using shadow information 138
6.5.3 Modelling 138
6.5.4 Shadow velocity measurement performance 139
6.5.5 Bright signature velocity performance 141
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6.5.6 Shadow centroid measurement accuracy 142
6.6 Shadow Properties 142
6.6.1 Introduction 142
6.6.2 Target motion effects on shadows 143
6.6.3 Contrast calculations 144
6.6.4 Contrast prediction tool 146
6.6.5 Clutter background 150
6.6.6 Polarisation 152
6.6.7 Effects of terrain slope 153
6.6.8 DTED Information 156
6.6.9 Conclusions 157
7 Polarisation 158
7.1 Introduction 158
7.2 Polarisation properties 159
7.3 Available Data 161
7.3.1 The MRMS seeker 162
7.3.2 The MEMPHIS radar 163
7.3.3 The Enhanced Surveillance Radar 164
7.3.4 Target sampling 168
7.4 Polarisation Conversion 169
7.4.1 Introduction 169
7.4.2 Theory 169
7.4.3 Testing 170
7.5 FGAN Analysis 173
7.5.1 Odd/Even comparison 173
7.5.2 Linear polarisations 175
7.6 MRMS Analysis 177
7.6.1 TCR analysis 177
7.6.2 TCR effects on the Residual False Object Density 178
7.7 ESR Analysis 180
7.7.1 TCR analysis 180
7.7.2 Feature analysis 180
7.8 Results Summary 187
7.8.1 Even and odd polarisation 187
7.8.2 Circular and linear polarisation 188
7.8.3 Effects on performance 188
7.9 Conclusions 189
7.10 Future Work 190
8 Real-Beam ATR 191
8.1 Introduction 191
8.2 Sensor Fused Munition outline 191
8.3 Understanding the system 192
8.3.1 Sensor Fused Munition Review 192
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8.4 Millimetre Wave Radar 194
8.4.1 SFM Radar Geometry 195
8.4.2 Radar Hardware 199
8.4.3 Radar Modelling 204
8.5 Test scenarios 206
8.5.1 Single Channel Radar Techniques 207
8.5.2 1D High Range Resolution (HRR) imaging 207
8.5.3 2D Adaptive Thresholding 209
8.5.4 Height detection 212
8.5.5 Multi-channel ATR 216
8.5.6 Monopulse Tests 219
8.5.7 Monopulse Height Detector 226
8.5.8 Scene with trees and target 232
8.5.9 Monopulse Accuracy 236
8.5.10 Conclusions 237
9 Conclusions & Future Work 238
9.1 Conclusions 238
9.2 Future work 240
References 242
A Published papers 247
A.1 Multi-Spectral Target Detection Fusion 247

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List of abbreviations

ADC Analogue to Digital Converter
ADU Air Defence Unit
APC Armoured Personnel Carrier
ATR Automatic Target Recognition
BBC British Broadcasting Corporation
CAD Computer-Aided Design
CDAA Context Data Aided Acquisition
CEP Circular Error Probable
CFAR Constant False Alarm Rate
CIF Composite Image Formation
CLTG Closed-Loop Terminal Guidance
CNR Clutter to Noise Ratio
COTS Commercial Off The Shelf
CW Continuous Wave
DBS Doppler Beam Sharpening
DDS Direct Digital Synthesis
DMS Dual Mode Seeker
DRO Dielectric Resonant Oscillator
DTED Digital Terrain Elevation Data
EM Electromagnetic
EO Electro-Optic
EPSRC Engineering and Physical Sciences Research Council
ESR Enhanced Surveillance Radar
FFT Fast Fourier Transform
FIBUA Fighting In Built-Up Areas
FM Frequency Modulation
FMCW Frequency Modulated Continuous Wave
FOV Field of View
FPGA Field Programmable Gate Array
GPS Global Positioning System
GUI Graphical User Interface
HRR High Range Resolution
IC Integrated Circuit
INS Inertial Navigation System
IR Infra-Red
ISAR Inverse Synthetic Aperture Radar
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JDAM Joint Direct Attack Munition
LDA Linear Discriminant Analysis
MBT Main Battle Tank
Multi-Frequency Experimental Monopulse High-resolution Interferometric
MEMPHIS
SAR
MMW Millimetre Wave
MRMS Multi-Role Modular Seeker
MTI Moving Target Indication
NATO North Atlantic Treaty Organization
NSDP Normalised Standard Deviation of Power
PCA Principal Component Analysis
P Probability of detection
d
P Probability of false alarm
fa
PRF Pulse Repetition Frequency
PSF Point Spread Function
RCS Radar Cross Section
RDM Range-Doppler Map
RFOD Residual False Object Density
ROC Receiver Operating Characteristic
ROE Rules Of Engagement
SADARM Search And Destroy ARMor
SAR Synthetic Aperture Radar
SFM Sensor Fused Munition
SFW Sensor Fused Weapon
SNR Signal to Noise Ratio
SPG Self-Propelled Gun
SPTA Salisbury Plain Training Area
STALO Stable Local Oscillator
TCR Target to Clutter Ratio
TEL Transporter Erector Launcher
TRE Telecommunications Research Establishment
UCL University College London
U.S. United States
UAV Unmanned Aerial Vehicle
UHF Ultra High Frequency
USA United States of America
VHF Very High Frequency
WRF Waveform Repetition Frequency
WW World War
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