Tactical Persistent Surveillance Radar with Applications
Tactical Persistent Surveillance Radar with Applications introduces technologists to the essential elements of persistent surveillance of tactical targets from both a hardware and software point of view, using simple Mathcad, Excel and Basic examples with real data. It is based on the type of surveillance done by drones like Scan Eagle, Predator, Reaper, Global Hawk, and manned aircraft like U-2, ASTOR, and JSTARS as well as spacecraft. The general topic is cellphone and datalink intercept, ground moving target radar, synthetic aperture radar, navigation, tracking, electronic scanning and cueing electro-optical sensors for activity based surveillance. Examples are taken from a wide range of technologies and techniques including passive detection, radar detection, antenna monopulse, active electronic scanned antennas (AESA), moving target tracking (MTT), motion compensation, tactical target spectral characteristics, moving target detection (MTI), space time adaptive processing (STAP), synthetic aperture radar (SAR) imaging, change detection (CCD), and synthetic monopulse. Over 120 example applications programs are included in the appendices and as downloads as well as over 100 SAR and GMTI raw IQ data files. These allow the curious to experiment with their own parameters and notions to achieve a greater understanding of the underlying behaviors. Based on the author's 55-year experience in engineering design, leadership, teaching and consulting, this book is an essential text for researchers, advanced students and technologists working in radar and related fields in computing and aerospace system design.
Other keywords: tactical targets; GMTI; coherent radars; tactical persistent surveillance radar; sensor signal; synthetic aperture radar; radar noise
- Book DOI: 10.1049/SBRA524E
- Chapter DOI: 10.1049/SBRA524E
- ISBN: 9781785616501
- e-ISBN: 9781785616518
- Page count: 706
- Format: PDF
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Front Matter
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1 Persistent tactical surveillance elements
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Obviously the applications mentioned in this chapter are just a sampling of radar based persistent surveillance. Also, the descriptions have left out many details necessary for understanding, analysis and design. Some of the basics will be discussed in the chapters that follow. Hopefully, the reader will have a good intuitive feel for all the important aspects of Intercept, GMTI and SAR by the end of this introductory book. The references and appendices will provide more detail on many of the topics in this book.
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2 What coherent radars do
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Everything from your house electricity to cosmic rays involves electromagnetic energy. There is electromagnetic radiation bathing us all the time from your electric blanket to TV to cellphones to radioactive decay of the bricks in your house to cosmic rays. Each has its own characteristic oscillation frequency and corresponding wavelength related by the velocity of light. Figure 2.1 shows much of the electromagnetic spectrum including the general location of frequency and source of emissions in that band. In addition the energy per photon increases as the wavelength gets shorter. So even though it is easy to feel those big fat photons coming out of an open fire or oven, the much shorter wavelengths have far more energy to penetrate most materials. Nonetheless, all of these wavelengths can carry significant energy. Radars are limited in the same way as your eye but, with significant signal processing and high signal to noise and interference ratios (SNIR), dramatic improvements in accuracy and acuity can be achieved. This is enabled by use of coherent processing not available to the naked eye.
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3 Nature of returns from the surface and tactical targets
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In a military context, the objective is to automatically detect tactical vehicles and dismounts at beyond visual range such as those in Figure 3.1, while eliminating all the other uninteresting movers. It is easy to find movers; what is hard is to find only the movers of tactical interest. There are numerous moving targets detectable in any significant FOR. They include people, insects, projectiles, missiles, animals, cars, trucks, trains, fences, power lines and suspended cables, leaves on trees and grass, ventilators, fans, clouds, rain, helicopters, UAVs, etc. What distinguishes many of these is that, although they have short-term movements and RCS that are similar to targets of interest, their ground coordinates do not change much. Usually a ground target must be observed for many seconds before its ground coordinates have changed enough for unequivocal discrimination. Even aircraft that have high ground speeds require seconds of observation for discrimination and trajectory determination. Trajectory discrimination over tens of seconds allows the sorting of projectiles from insects and birds, fixed wing aircraft from helicopters, wheeled vehicles from tracked vehicles, etc. These multiple observations if statistically independent are often called “Looks".
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4 Sensor signal and data processing
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The suite of microwave and RF apertures in a fighter, surveillance aircraft or spacecraft might be as many as 20 apertures distributed throughout the vehicle performing radar, data link, navigation, missile warning, direction finding, jamming or other functions over a frequency range covering several decades. There are apertures distributed over the platform that point forward and aft, right and left, as well as up and down. Some apertures will be shared for communications, radio navigation and identification (CNI) as well as identification, friend or foe (IFF) due to compatible frequencies and geometries. Data links such as JTIDS/Link 16 and Link 22 can share apertures with GPS and L-band satellite communications (L-SATCOM). There also may be dedicated data link apertures. EW apertures must be broadband by nature and can be shared with radar warning receivers (RWR), radar auxiliaries and some types of CNI.
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5 Noise in radar and intercept systems
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Noise of all kinds limits ultimate detection performance for all electromagnetic sensor systems whether cosmic, UV, visible, IR, microwave or RF. Thermal noise is often thought of as the ultimate limitation on detection and tracking but often it is self-noise in a sensor system, which limits performance. Low-frequency systems with seemingly very low noise figures (NF) are often limited by sky noise from the residual of the “Big Bang,”from auroras and from what used to be called “Monkey Talk.”Great strides have been made in signal processing in the last 50 years. This is the result of dramatic improvements in signal processing hardware as well as a better theoretical understanding. In spite of this, many systems provide disappointing performance. The two main reasons for shortfalls are sensor signal processor self-noise and the physical world's continuing refusal to be normal (Gaussian). Although we have undreamed of device performance and number smashing today, we are inevitably forced by economics to limit hardware complexity that gives rise to significant self-noise. Noise and interference in the real world are “bursty,”“lumpy,”discrete, not stationary, anomalous and even malevolent! This chapter is an introduction to analog and digital signal processing self-noise analysis and heuristic means to control ill-behaved internal and external noise.
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6 The GMTI idea
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Ground or surface moving target detection (often called ground moving target indication or GMTI) consists of radar or EO detection of humans or tactical vehicles moving on or near the earth's surface. Animals and humans have little difficulty detecting movement and sorting unimportant movements from an important movement at short range. This is the result of hundreds of millions of years of selective evolution. For example, the frog's eye is especially adapted to detect and react to a fly-sized object moving through its field of vision. It is so good that its tongue is on the move to where the fly will be (not where it is) in less than 100 ms. Sadly, radars and EO sensors are not nearly that good over their ranges of operation (much longer than a frog's tongue!). In the following sections, the fundamental characteristics for discrimination of ground mover RCS, Doppler signature and clutter will be discussed.
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7 The synthetic aperture radar idea
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Another way to detect slow-moving tactical targets is by means of HRM coupled with some form of change detection between multiple images. The change detection methods are coherent change detection (CCD) and shadow detection, noncoherent change detection (NCD), video SAR, inverse SAR (ISAR) and synthetic monopulse. Each of these will be discussed but first an understanding of conventional SAR is required. Often, fast(er) moving targets and slow-moving targets and SAR maps are acquired by the same waveform as described at the end of Chapter 6. The separate target types are usually separated by filtering.
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Appendices
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The following software appendices give details the items of software in Chapters 1-7.
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Back Matter
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Supplementary material
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Supplementary Files for this book
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- Over 120 example applications programs are included here as downloads as well as over 100 SAR and GMTI raw IQ data files. These allow the curious to experiment with their own parameters and notions to achieve a greater understanding of the underlying behaviors described in the book.There are counterpart Adobe Acrobat files of most of the programs with output for a user to read first.
Please note, these software appendices are for information only and the Publisher accepts no liability.
For each chapter there is a single zipped file within the larger zipped file.
If you have any problems with these files, please contact us at [email protected].
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643.4871397018433MB
- Over 120 example applications programs are included here as downloads as well as over 100 SAR and GMTI raw IQ data files. These allow the curious to experiment with their own parameters and notions to achieve a greater understanding of the underlying behaviors described in the book.There are counterpart Adobe Acrobat files of most of the programs with output for a user to read first.
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