Principles of Modern Radar

Transcription

1 Principles of Modern Radar Vol. I: Basic Principles Mark A. Richards Georgia Institute of Technology James A. Scheer Georgia Institute of Technology William A. Holm Georgia Institute of Technology PUBLiSH]J etinc Raleigh, NC scitechpub.com

2 Preface xvii Publisher Acknowledgments xxiv Editors and Contributors List of Acronyms xxxi List of Common Symbols xxvii xxxiv Overview 1 Introduction and Radar Overview Introduction The Radar Concept The Physics of EM Waves Interaction of EM Waves with Matter Basic Radar Configurations and Waveforms Noise, Signal-to-Noise Ratio, and Detection Basic Radar Measurements Basic Radar Functions Radar Applications Organization of This Text Further Reading References Problems 56 2 The Radar Range Equation Introduction Power Density at a Distance R Received Power from a Target Receiver Thermal Noise Signal-to-Noise Ratio and the Radar Range Equation Multiple-Pulse Effects Summary of Losses Solving for Other Variables 72 ix

3 X Contents 2.9 Decibel Form of the Radar Range Equation Average Power Form of the Radar Range Equation Pulse Compression: Intrapulse Modulation A Graphical Example Clutter as the Target One-Way (Link) Equation Search Form of the Radar Range Equation Track Form of the Radar Range Equation Some Implications of the Radar Range Equation Further Reading References Problems 85 3 Radar Search and Overview of Detection in Interference Introduction Search Mode Fundamentals Overview of Detection Fundamentals Further Reading References Problems 112 External Factors 4 Propagation Effects and Mechanisms Introduction Propagation Factor Propagation Paths and Regions Atmospheric Attenuation and Absorption Atmospheric Refraction Turbulence Exploiting the Ionosphere Diffraction Multipath Skin Depth and Penetration: Transmitting Through Walls Commercial Simulations Summary and Further Reading References Problems 163

4 xi 5 Characteristics of Clutter Introduction and Definitions General Characteristics of Clutter Clutter Modeling Concluding Remarks Further Reading References Problems Target Reflectivity Introduction Basic Reflection Physics Radar Cross Section Definition Three Scattering Regimes High-Frequency Scattering Examples Further Reading References Problems Target Fluctuation Models Introduction Radar Cross Section of Simple Targets Radar Cross Section of Complex Targets Statistical Characteristics of the RCS of Complex Targets Target Fluctuation Models Doppler Spectrum of Fluctuating Targets Further Reading References Problems Doppler Phenomenology and Data Acquisition Introduction Doppler Shift The Fourier Transform Spectrum of a Pulsed Radar Signal Why Multiple Pulses? 286

5 8.6 Pulsed Radar Data Acquisition Doppler Signal Model Range-Doppler Spectrum for a Stationary Radar Range-Doppler Spectrum for a Moving Radar Further Reading References Problems 303 i/i^am Subsystems 9 Radar Antennas Introduction Basic Antenna Concepts Aperture Tapers Effect of the Antenna on Radar Performance Monopulse Reflector Antennas Phased Array Antennas Array Architectures Further Reading References Problems Radar Transmitters Introduction Transmitter Configurations Power Sources and Amplifiers Modulators Power Supplies Transmitter Impacts on the Electromagnetic Environment Operational Considerations Summary and Future Trends Further Reading References Problems Radar Receivers Introduction Summary of Receiver Types 392

6 xiii 11.3 Major Receiver Functions Demodulation Receiver Noise Power Receiver Dynamic Range Analog-to-Digital 11.8 Further Reading References Problems 415 Data Conversion Radar Exciters Introduction Exciter-Related Radar System Performance Issues Exciter Design Considerations Exciter Components Timing and Control Circuits Further Reading References Problems The Radar Signal Processor Introduction Radar Processor Structure Signal Processor Metrics Counting FLOPs: Estimating Algorithm Computational Requirements Implementation Technology Fixed Point versus Floating Point Signal Processor Sizing Further Reading References Problems 491 PART IV Signal and Data Processing 14 Digital Signal Processing Fundamentals for Radar Introduction Sampling Quantization Fourier Analysis 506

7 14.5 The z Transform Digital Filtering Random Signals Integration Correlation as a Signal Processing Operation Matched Filters Further Reading References Problems Threshold Detection of Radar Targets Introduction Detection Strategies for Multiple Measurements Introduction to Optimal Detection Statistical Models for Noise and Target RCS in Radar Threshold Detection of Radar Signals Further Reading References Problems Constant False Alarm Rate Detectors Introduction Overview of Detection Theory False Alarm Impact and Sensitivity CFAR Detectors Cell Averaging CFAR Robust CFARs Algorithm Comparison Adaptive CFARs Additional Comments Further Reading References Problems Doppler Processing Introduction Review of Doppler Shift and Pulsed Radar Data Pulsed Radar Doppler Data Acquisition and Characteristics 627

8 xv 17.4 Moving Target Indication Pulse-Doppler Processing Clutter Mapping and the Moving Target Detector Pulse Pair Processing Further Reading References Problems Radar Measurements Introduction Precision and Accuracy in Radar Measurements Radar Signal Model Parameter Estimation Range Measurements Phase Measurement Doppler and Range Rate Measurements RCS Estimation Angle Measurements Coordinate Systems Further Reading References Problems Radar Tracking Algorithms Introduction Basics of Track Filtering Kinematic Motion Models Measurement Models Radar Track Filtering Measurement-to-Track Data Association Performance Assessment of Tracking Algorithms Further Reading References Problems Fundamentals of Pulse Compression Waveforms Introduction Matched Filters Range Resolution 782

9 20.4 Straddle Loss Pulse Compression Waveforms Pulse Compression Gain Linear Frequency Modulated Waveforms Matched Filter Implementations Sidelobe Reduction in an LFM Waveform Ambiguity Functions LFM Summary Phase-Coded Waveforms Biphase Codes Polyphase Codes Phase-Code Summary Further Reading References Problems An Overview of Radar Imaging Introduction General Imaging Considerations Resolution Relationships and Sampling Requirements Data Collection Image Formation Image Phenomenology Summary Further Reading References Problems 890 Appendix A: Maxwell's Equations A.l Maxwell's Equations 893 A.2 The Ubiquitous db 895 and Decibel Notation 893 A.3 Reference 897 Appendix B: Answers to Selected Problems 899 Index 905