Taylor James D. (ed.) Ultra-wideband radar technology

CRC Press, 2000. — 688 p.Ultra-Wideband Radar Technology is a guide to the future of radar by an international team of experts. They present the problems, solutions, and examples of UWB radar remote sensing. Chapters discuss the theory and ideas for future systems development, and show the potential capabilities. The writers present concepts such as the differences between UWB and conventional radars, improving over-resolved target detection, receivers and waveforms, micropower systems, high power switching, and bistatic radar polarimetry.Finding comparable information elsewhere might require consulting hundreds of other books, technical journals, and symposium proceedings. Ultra-Wideband Radar Technology offers a unique opportunity to explore the theory, applications, and technology of UWB radar within a single source.Main Features of Ultra-Wideband (UWB) Radars and Differences from Common Narrowband Radars: written by Dr. Igor Immoreev of the Moscow State Aviation Institute in Russia. He explains how UWB signals will produce effects not encountered in conventional low-resolution radar. This leads to the concept of signal spectral efficiency. Life is further complicated because fine range resolution turns the target into a series of point returns from scattering centers and creates major signal processing and target detection problems. A direct result of the time-variable UWB antenna and target characteristics is a time-dependent radar range equation.Improved Signal Detection in UWB Radars by Dr. Igor Immoreev, expands the concepts of Chapter 1. He presents an approach to detecting over-resolved targets by correlating multiple returns over an estimated spatial window about the physical size of the target. This solves the problem of reduced UWB radar returns from numerous scattering centers; however, it will present a new way of considering radar reflection characteristics and target radar cross section specifications.High-Resolution Ultra-Wideband Radars by Dr. Nasser J. Mohammed, of the University of Kuwait, presents a concept for identifying UWB radar targets. This method involves correlating the series of target returns against a library of known target signals. There is a close relationship with ideas of Chapter 2.Ultra-wideband Radar Receivers by James D. Taylor examines some major theoretical issues in receiver design. This chapter starts with concepts of digitizing and recording impulse signals in a single pass, which is a major problem area building impulse radars for material recognition. Pulse compression is another UWB radar technique that has potential applications where fine range resolution is needed at long ranges. Practical guidance for estimating the bandwidth of UWB signals is given by an explanation of the spectrum of pulse modulated sinewaves. Performance prediction for UWB systems remains a problem area, and the solution may have to be specific to radar systems and waveforms. While the question cannot be answered with a single neat equation, I have provided an approach to performance estimation as a starting point. Chapter 4 is complementary to Chapters 1, 2, and 3.Compression of Wideband Returns from Overspread Targets by Dr. Benjamin C. Flores and Roberto Vasquez, Jr., of the University of Texas at El Paso, provides a look at how to use pulse compressed signals in radio astronomy. While the ambiguity function was mentioned in Chapter 4, this chapter shows what happens to long-duration pulse-compressed signals when there are time or frequency shifts caused by target motion.The Micropower Impulse Radar by James D. Taylor and Thomas E. McEwan, examines low-power system technology for short-range applications. Recent advances in integrated circuit technologies will provide a wide variety of short-range sensors and communication systems. Using micropower radar techniques can put radar sensors in places never thought of before.Ultra-wideband Technology for Intelligent Transportation Systems by Dr. Robert D. James and Jeffrey B. Mendola, of the Virginia Tech Transportation Center, and James D. Taylor, shows how future smart highway systems can use UWB signals. Short-range sensing and communications are two requirements for watching traffic conditions and then communicating instructions to vehicles. Additionally, we can expect to see some form of radar installed in automobiles and trucks for station maintenance and collision avoidance with other vehicles in traffic. Automotive radar and communications may be a primary UWB development area in the near future; however, it will require a large effort to build smart highways and vehicles. The question of infrastructure design, systems standards, highway control schemes, communication protocols and links, and other issues must be settled before any widespread smart highway system can be built. This chapter raises the potential for vehicle tracing and location, which may raise some serious constitutional privacy issues in a democratic country.Design, Performance, and Applications of a Coherent UWB Random Noise Radar by Dr. Ram Narayanan, Yi Xu, Paul D. Hoffmeyer, and John O. Curtis, shows how bandwidth alone determines range resolution. Dr. Narayanan and his University of Nebraska associates built and demonstrated a continuous random noise signal radar. By preserving the random noise signal in a delay line, this experimental 1 GHz radar achieved spatial resolution of 15 cm. Such a concept would be potentially valuable for building a stealthy, low probability of intercept radar or for operating at low power levels to avoid interference with other systems.New Power Semiconductor Devices for Generation of Nano- and Subnanosecond Pulses by Dr. Alexei Kardo-Syssoev, of the Ioffe Physical-Technical Institute in St. Petersburg, Russia, describes the fundamentals of high-power impulse generation. Producing high-power impulse signals involves suddenly moving large amounts of current, which implies special switches that close or open in picoseconds. This chapter explains the theory of drift step recovery diodes and other high-speed switching devices. Dr. Kardo-Syssoev is the head of the Pulse Systems Group of the Ioffe Physical-Technical Institute. His engineers have provided advanced semiconductor switching devices to SRI International and other American organizations.Fourier Series-Based Waveform Generation and Signal Processing in UWB Radar by Dr. Gurnam S. Gill, of the Naval Post Graduate School in Monterey, California, presents another approach to generating ultra-wideband waveforms. While high-speed switching techniques are a straightforward approach to impulse generation, repeatability remains an issue. There is always a suspicion that each impulse may be slightly different from the others, which will affect signal processing. Generating UWB signals by adding many different waveforms together offers a more flexible approach to building high-power UWB radar systems, especially ones that need a highly accurate and coherent waveform.High-Resolution Step-Frequency Radar by Dr. Gurnam S. Gill, shows how to build a UWB radar using long-duration narrowband radar signals. Processing many narrowband returns can give the same result as an instantaneous UWB signal. This is an approach to avoiding the regulatory issues that limit high-power UWB system development. Interference with narrowband systems may force the designer to notch out certain restricted frequency bands before the system can be used legally. Dr. Gill develops the theory of using step-frequency waveforms, which transmit many long-duration, narrowband signals and then process them to achieve the effect of a UWB signal.CARABAS Airborne SAR by Dr. Lars Ulander, Dr. Hans Hellsten, and James D. Taylor, describes a step-frequency UWB radar developed and tested by the Swedish Defence Ministry. The Coherent All Radio Band System (CARABAS) demonstrates how to build a highresolution SAR using step-frequency radar. CARABAS demonstrated both high-resolution imaging and foliage penetration expected from VHF signals.Ultra-Wideband Radar Capability Demonstrations by James D. Taylor, describes the state of the art in UWB radar for precision imaging, finding targets hidden by foliage, and detecting buried mines. ARPA-sponsored demonstrations showed the potential of high-power UWB radar as a practical sensing system for military applications. ERIM International, the Lawrence Livermore National Laboratory (LLNL), SRI International, MIT Lincoln Laboratory, and the Army Research Laboratory programs show the capabilities and problems of UWB radar.Bistatic Radar Polarimetry by Dr. Anne-Laure Germond, of the Conservertoire National des Arts et Metiers in Paris, France, and her colleagues Dr. Eric Pottier, and Dr. Joseph Saillard, presents a new approach to understanding and analyzing bistatic radar signals. Bistatic radar will be an important future technology for detecting small radar cross section targets. Using side-scattered energy for target detection has several potential advantages, including the ability to locate transmitters in protected refuges and move the receiver freely over areas in which it would be dangerous to radiate. Polarimetric radars using orthogonally polarized signals to increase target detection will be a major future radar trend. Analyzing the measured polarization shifts of reflected radar signals may provide a future method for passive target identification. The future of remote sensing may be polarimetric UWB radar.