ABSTRACT
Over the last two decades a broad range of science, engineering, and related disciplines have used the penetration properties of electromagnetic waves to probe optically nontransparent material media. In recent years, the progress in electromagnetic sciences along with the revolution in microelectronics and computers brought signiŽcant sophistication in material-penetrating radar imagery. Many such advances use ultrawideband (UWB) radar technologies that gain in spatial resolution and depth of penetration into
CONTENTS
12.1 Introduction ........................................................................................................................ 389 12.2 Operation and Design Principles .................................................................................... 390
12.2.1 ClassiŽcation Based on Material Operational Environment ........................... 390 12.2.2 Major Performance Measures of Material-Penetrating Radar ........................ 392 12.2.3 System-Level Design Constraints and Trade-Offs ............................................ 393
12.3 Implementation Methodology ......................................................................................... 394 12.3.1 Methods to Support Broadband Operation ....................................................... 395 12.3.2 Measurement of Radar Target Features ............................................................. 397 12.3.3 Antenna Operational Conditions ........................................................................ 397
12.4 Radar Imaging Methods ...................................................................................................400 12.4.1 Signal Processing Techniques ..............................................................................400 12.4.2 Radar Image Display Techniques ........................................................................402 12.4.3 Image Interpretation .............................................................................................. 402
12.5 SAR Imaging Scheme ........................................................................................................404 12.5.1 UWB SAR with Antennas Operating in Far-Field Conditions .......................404 12.5.2 Forward-Looking UWB SAR for Detecting Objects in Vegetation ................405 12.5.3 Side-Looking UWB SAR for Landmine Detection ............................................ 407
12.6 Inverse SAR Imaging Schemes ........................................................................................409 12.6.1 Tracking Moving Targets with Through-the-Wall ISAR Technology ............409 12.6.2 ISAR for High-Resolution Imaging of Rotary Moving Targets ...................... 410
12.7 Imaging with Limited-Size Physical Apertures ............................................................ 411 12.8 Medical UWB Radar Interferometric Imaging .............................................................. 414 12.9 Conclusion .......................................................................................................................... 416 References ..................................................................................................................................... 417
many natural and artiŽcial materials. This chapter presents the key operational principles and design concepts of material-penetrating UWB radar methods and imaging. We place special emphasis upon system-level analysis and implementation issues for the major radar building blocks and imaging techniques with synthetic and physical apertures. The results of several real-world projects illustrate the principles. Most examples come from the authors’ personal practice. The authors sincerely acknowledge the materials-including some materials that are not yet published-provided kindly by their collaborators, sponsors, and colleagues. The authors also thank the IEEE, Springer, and Federal Railroad Administration for granting reprint permissions.
