![]()
1
Introduction to Ultrawideband Radar Applications and Design
James D. Taylor
CONTENTS
1.1 Introduction and Objectives
1.1.1 Concept of Ultrawideband Radar
1.1.2 Editorial Objectives
1.2 Origin of UWB Radar
1.2.1 My Association with UWB Radar
1.2.2 Bandwidth and Radar Range Resolution
1.2.3 Early Demonstrations of UWB Radar
1.3 UWB Radar Resources
1.4 UWB Radar Definitions and Regulations
1.4.1 Early History of UWB Radar
1.4.2 Standard Definitions of UWB Radar
1.4.3 Bandwidth Designations and Definitions
1.5 Time and Frequency Domain Analysis in UWB Radar
1.6 Nonsinusoidal Signal Propagation
1.6.1 Background
1.6.2 Example of Gaussian Pulse Transformation during Transmission and Reception
1.6.3 Conclusions on Gaussian Pulse Signal Propagation
1.7 UWB Radar: Future Trends and Applications
1.7.1 Open-Space Measurement and Surveillance
1.7.2 Material-Penetrating Remote-Sensing Application
1.7.3 Medical Measurements and Imaging
1.7.4 Security
1.7.5 Military Remote-Sensing Applications
1.8 Future Directions in UWB Radar Development
1.8.1 Optimization of UWB Antenna Array Geometry
1.8.2 Synchronization of Antenna Array Signals
1.8.3 Improvements in Receiver Signal-to-Noise Ratios
1.8.4 Multistatic Radar
1.8.5 Higher Order Signal Processing to Augment Imaging and Target Identification
1.9 Architecture of Future UWB Radars
1.10 Conclusions
References
1.1 Introduction and Objectives
1.1.1 Concept of Ultrawideband Radar
The term ultrawide band (UWB) describes a radar s ystem with an effective signal bandwidth that is a large percentage of the center frequency (20%–25%). This wi de bandwidth gives the radar systems a small spatial resolution (centimeter to millimeter) measurements and good imaging capabilities. UWB radars use a varie ty of signal formats, including short-duration pulses (impulses), random noise signals, step frequency coding, and pulse sequence coding, to achieve wide bandwidths. The fine spatial resolution of these radars can provide precision-range measurements for locating and imaging applications. In the following chapters, you will find examples of UWB radar systems in specia l applications requiring fine spatial resolution measurement and in penetration of materials for construction, geophysical surveying, security, and medical purposes [1,2].
1.1.2 Editorial Objectives
The writers prepared this book to give engineers and technical managers practical information about the latest UWB radar theory through real-world examples. You will find descriptions of systems that demonstrate new techniques and possible development directions for advanced UWB radars. Explanatory material and basic useful information have been added to make the book readable for newcomers. You will find chapters devoted to history, time-domain propagation theory, governmental regulations, and propagation in solid media. Some chapters describe UWB radar applications and implementations with example s, showing solutions to practical problems and demonstrating new radar sensing capabilities. You will also find practical examples of UWB radar, such as through-wall imaging, large-target backscattering effects, ground permittivity estimation, medical applications, and measurement of small movements of large buildings. These special applications and the theory supporting their design demonstrate the theoretical principles of UWB radar. We hope these descriptions of past accomplishments of the radar systems will pave the way for future concepts and practical applications.
1.2 Origin of UWB Radar
1.2.1 My Association with UWB Radar
During the late 1980s, I served as the director of Long Range Technology Planning at the U.S. Air Force Systems Command’s Electron ic Systems Division, Hanscom Air Force Base, Massachusetts, United States. My commanders directed me to use my judgment to identif y new technology trends that could affect future defense capabilities and requirements. This put me in touch with experts and new ideas from industry and academia.
Everybody recognized the threat from ballistic missiles, and the “Star Wars” S trategic Defense Initiative (SDI) program received all the h igh-level attention and funding. At the time SDI started, the first cruise missiles en tered the American and Soviet Union arsenals and presented a new threat to national security. Drawing on my experiences as an air defense artillery officer, I considered the cruise missile threat a major technical challenge. I approached my commander with the implications of cruise missile defense for the future mission of the Electronic Systems Division and suggested investigating the problems in detecting cruise missiles flying at low altitudes.
My analysis of the problem indicated that detecting low-flying and small radar cross-section (RCS) targets at long ranges would require (1) airborne radar systems with a look-down capability because of the radar horizon and (2) radar spatial resolution in the order of the physical size of the target (0.1–10 m). Fine spatial resolution implied a large bandwidth and brought the additional adv antage of target identification by analysis of the return signal and possible recognition by imaging. More bandwidth meant more information and grea...
