MARITIME FORWARD SCATTER RADAR by Liam Yannick Daniel A thesis submitted to the University of Birmingham for the degree of DOCTOR OF PHILOSOPHY Electronic, Electrical and Systems Engineering University of Birmingham May 2016 University of Birmingham Research Archive e-theses repository This unpublished thesis/dissertation is copyright of the author and/or third parties. The intellectual property rights of the author or third parties in respect of this work are as defined by The Copyright Designs and Patents Act 1988 or as modified by any successor legislation. Any use made of information contained in this thesis/dissertation must be in accordance with that legislation and must be properly acknowledged. Further distribution or reproduction in any format is prohibited without the permission of the copyright holder. ABSTRACT This thesis is dedicated to the study of forward scatter radar (FSR) in the marine environment. FSR is a class of bistatic radar where target detection occurs at very large bistatic angle, close to the radar baseline. It is a rarely studied radar topology and the maritime application is a completely novel area of research. The aim is to develop an easily deployed buoy mounted FSR network, which will provide perimeter protection for maritime assets—this thesis presents the initial stages of investigation. It introduces FSR and compares it to the more common monostatic/bistatic radar topologies, highlighting both benefits and limitations. Phenomenological principles are developed to allow formation of forward scatter signal models and provide deeper understanding of the parameters effecting the operation of an FSR system. Novel FSR hardware has been designed and manufactured and an extensive measurement campaign undertaken. The outcome of this was the creation of the first comprehensive maritime FSR target and clutter signal database—results from which have been shown with preliminary analysis. Alongside experimental work, a sea surface model has been produced in order to estimate the effects of wave blocking in high sea states and assess FSR performance in these conditions. DEDICATION Firstly, I would like to express my gratitude to my academic supervisors Prof. Cherniakov and Dr. Gashinova. Thank you for your knowledge and expertise and your continuous support and friendship both during my Ph.D and in the times since. I want to thank Dr. Edward Hoare, a constant source of useful information, appalling jokes and a good friend. I appreciate all your help and advice, both in relation to work (a good engineer would make one) and life (what’s the worst that can happen). Mother, I know you thought you would never see this thesis, Dad you knew it would come in the end and Nan, I know you have been holding on for this for a while. Thank you all for sticking with it and supporting me so extensively, both morally and monetarily… I got there in the end! Louise, my very patient wife. I think this PhD was more stressful for you than me (sorry)! You have provided me with limitless support throughout, taking up the slack during busy times and for this I am truly grateful—love you. Finally, I dedicate this thesis to my son Seth, you are genuinely the most awesome little man I have ever had the pleasure to meet. You were the inspiration to finish this thesis, I hope I make you proud. ACKNOWLEDGEMENTS This PhD study was funded by the Engineering and Physical Sciences Research Council (EPSRC). CONTENTS 1 Introduction ............................................................................................................. 1 2 Radar Principles ...................................................................................................... 7 2.1 Monostatic and Bistatic Radar ............................................................................. 7 2.2 Antenna Parameters ............................................................................................. 8 2.2.1 Rectangular Aperture Antenna .................................................................... 12 2.2.2 Elliptical and Circular Aperture Antennas .................................................. 14 2.3 Target Radar Cross Section ............................................................................... 18 2.3.1 Radar Cross Section Fluctuations ............................................................... 20 2.4 The Radar Equation ........................................................................................... 22 2.5 Range Resolution ............................................................................................... 25 2.6 Angular Resolution ............................................................................................ 28 2.7 The Doppler Shift and Doppler Resolution ....................................................... 29 2.8 Clutter ................................................................................................................ 30 2.8.1 Normalised area and volume clutters .......................................................... 34 2.9 Detection of Signals in Noise – The Matched Filter Receiver .......................... 34 2.9.1 Matched Filter for Non – White Noise........................................................ 37 2.9.2 Matched Filter Relation to Correlation ....................................................... 37 2.10 Forward Scatter Radar Overview .................................................................. 38 2.10.1 Topology ..................................................................................................... 38 2.10.2 Forward Scatter Radar Cross Section.......................................................... 39 2.10.3 Spatial Resolution Parameters in FSR ........................................................ 42 2.10.4 Frequency Resolution and Doppler Shift in Forward Scatter Radar ........... 44 3 Forward Scatter Radar for Surface Targets ........................................................... 47 3.1 Phenomenology of Doppler Forward Scatter Radar.......................................... 47 3.1.1 The Forward Scatter Effect ......................................................................... 48 3.1.2 Relation of Shadow Radiation/Forward Scatter Effect to Forward Scatter Cross Section ............................................................................................... 51 3.1.3 Forward—Bistatic Scattering Boundary ..................................................... 54 3.1.4 Target Signature Formation in Forward Scatter Radar ............................... 56 3.1.4.1 Target Phase/Doppler Signature ............................................................. 57 3.1.4.2 Target Signature Envelope – The Effect of Forward Scatter Cross Section .................................................................................................... 63 3.1.5 Verification of Forward Scatter Phenomenon in a Controlled Environment—Experimental study in anechoic chamber ........................... 70 3.1.6 Effect of Target Dimension on Scattering ................................................... 74 3.2 Forward Scatter Radar Power Budget for Surface Targets ............................... 75 3.2.1 Power Budget in Free Space ....................................................................... 76 3.2.2 Power Budget in the Two-Ray Path Model ................................................ 78 3.2.2.1 Leakage Signal ....................................................................................... 79 3.2.2.2 Target Signal .......................................................................................... 84 3.2.2.3 Modified Reflection Co-Efficient for Sea Surface Scattering ................ 88 3.3 Summary of FSR for Surface Targets ............................................................... 91 4 Maritime Forward Scatter Radar ........................................................................... 92 4.1 Maritime Forward Scatter Radar Network Concept .......................................... 92 4.2 Forward Scatter Radar Prototype Experimental Equipment ............................. 94 4.2.1 Transmitter and Receiver Design ................................................................ 96 4.2.1.1 Phase Noise Considerations ................................................................. 100 4.2.2 Antennas .................................................................................................... 102 4.2.3 Wideband and Ultra-wideband Hardware Development .......................... 103 4.2.4 Mock Buoy ................................................................................................ 106 4.3 Co-operative Target ......................................................................................... 107 4.4 Maritime Experimental Test Sites ................................................................... 107 4.4.1 Langstone Harbour .................................................................................... 108 4.4.2 Coniston Water .......................................................................................... 108 4.4.3 Other Test Sites ......................................................................................... 109 4.5 Ground Truth and Environmental Measurements ........................................... 109 4.5.1 Weather and Sea State ............................................................................... 109 4.5.2 Video and Photo Imagery .......................................................................... 110 4.5.3 Trajectory and Topology