Introduction to Sensors for Ranging and Imaging. Dr. Graham Brooker S SCITEOT. publishmefinc. SciTech Publishing, Inc Raleigh, NC

Transcription

1 Introduction to Sensors for Ranging and Imaging Dr. Graham Brooker S SCITEOT publishmefinc. SciTech Publishing, Inc Raleigh, NC

2 Introduction to Sensors for Ranging and Imaging Chapter 1 Chapter 2 Introduction to Sensing 1.1 Introduction Active Sensors Passive Sensors A Brief History of Sensing Sonar Radar Lidar Passive Infrared Sensing Sensor Systems Frequency Band Allocations for the Electromagnetic Spectrum 1.6 Frequency Band Allocations for the Acoustic Spectrum References 21 Signal Processing and Modulation 2.1 The Nature of Electronic Signals Static and Quasi-Static Signals Periodic and Repetitive Signals Transient and Quasi Transient Signals Noise Thermal Noise Noise Power Spectrum for Thermal Noise Shot Noise Noise Power Spectrum for Shot Noise /f Noise Avalanche Noise Signals Signals and Noise in the Frequency Domain The Fourier Series Sampled Signals Generating Signals in MATLAB Aliasing 37

3 VI Table of Contents 2.6 Filtering Filter Categories Butterworth Chebyshev Bessel Elliptic Filter Roll-off The Ear as a Filter Bank Analog Modulation and Demodulation Amplitude Modulation Frequency Modulation (FM) Linear Frequency Modulation Pulse Coded Modulation Techniques Pulse Amplitude Modulation Frequency Shift Keying Phase Shift Keying Stepped Frequency Modulation Convolution Linear Time Invariant Systems The Convolution Sum Worked Example: Pulsed Radar Echo Amplitude References 67 Chapter 3 IR Radiometers & Image Intensifies ' Introduction Thermal Emission Blackbody Radiation The Planck Function Properties of the Planck Function Confirmation of Stefan-Boltzmann and Rayleigh-Jean Laws Emissivity and Reflectivity Worked Example: Black Body Radiation from Human Body Detecting Thermal Radiation External Photoeffect Internal Photoeffect Photoconductive Detectors Photovoltaic Detectors Heating Bolometers Pyroelectric Sensors Thermopiles 84

4 VII 3.6 Performance Criteria for Detectors Responsivity Noise Equivalent Power (NEP) Detectivity and Specific Detectivity Noise Processes and Effects Applications Passive Ultraviolet Sensor (External Photoeffect) Radiation Thermometer (Internal Photoeffect: Thermopile) Passive Infrared Sensor (Internal Photoeffect: Pyroelectric) Crookes' Radiometer Introduction to Thermal Imaging Systems Scattering and Absorption Scanning Mechanisms and Arrays Micro-bolometer Arrays Key Optical Parameters Performance Measures for Infrared Imagers Detector Field of View Spatial Frequency Signal to Noise Ratio for a Point Target Worked Example: IRST System SNR Signal to Noise Ratio for a Target in Ground Clutter Noise Equivalent Temperature Difference (NETD) Example The Minimum Resolvable Temperature Difference (MRTD) Target Detection and Recognition Example of FLIR Detection Thermal Imaging Applications Image Intensifiers First Generation Tubes Second Generation Tubes Limitations of MicroChannel Plates Third Generation Tubes Spectral Characteristics of die Scene Time Gating MicroChannel Plates References 119 Chapter 4 Millimeter Wave Radiometers 4.1 Antenna Power Temperature Correspondence Example of Power Received from a Blackbody

5 4.2 Brightness Temperature Apparent Temperature Atmospheric Effects Attenuation Downwelling Radiation Upwelling Radiation Terrain Brightness Worked Example: Space-based Radiometer Temperature Contrast Antenna Considerations Beamwidth Efficiency Fill Ratio Receiver Considerations Mixer Implementations for Microwave Receivers Mixer Specifications Noise Figure The System Noise Temperature Radiometer Temperature Sensitivity Radiometer Implementation Total Power Radiometer Dicke Radiometer Performance Comparison between Radiometer Types Intermediate Frequency and Video Gain Requirements Worked Example: Anti Tank Submunition Sensor Design Radiometer Implementation Receiver Noise Temperature Minimum Detectable Temperature Difference Radiometric Imaging Image Processing Applications Airborne Scanned Millimeter Wave Radiometer Scanning Multi-channel Microwave Radiometer (SMMR) Ground Based Millimeter Wave Radiometers Low Visibility Imaging Concealed Weapon Detection Surveillance and Law Enforcement Medical Imaging Radio Astronomy Single Dish Telescopes 156

6 IX 4.16 References Telescope Arrays Applications 157 Chapter 5 Active Ranging Sensors Overview Triangulation Pulsed Time-of-Flight Operation Sensor Requirements Speed of Propagation The Antenna The Transmitter Radar Transmitters Underwater Sonar Transmitters Ultrasonic Transmitters Laser Transmitters The Receiver Pulsed Range Measurement Timing Discriminators Pulse Integration Time Transformation Other Methods to Measure Range Ranging using an Unmodulated Carrier Ranging using a Modulated Carrier Tellurometer Example The Radar Range Equation Derivation The db Form Worked Example: Radar Detection Calculation Receiver Noise Determining the Required Signal Level Pulse integration and the probability of detection The Acoustic Range Equation Example of Using the Acoustic Range Equation TOF Measurement Considerations Range Measurement Radar for a Cruise References 212 Chapter 6 Active Imaging Sensors Imaging Techniques Range-Gate limited 2D Image Construction 216

7 X Table of Contents 6.3 Beamwidth Limited 3D Image Construction Push-Broom Scanning Mechanical Scanning The Lidar Range Equation Lidar System Performance Direct Detection Direct Detection Photodiodes Heterodyne Detection Signal to Noise Ratio and Detection Probability Worked Example: Laser Radar Reflection from the Moon Digital Terrain Models Surface Models Digital Landscapes Thematic Visualization Geographic Information Systems D City Models Airborne Lidar Hydrography D Imaging Radar Systems Focused Beam Radar Imaging Lidar Imaging Jigsaw Foliage Penetrating Lidar Acoustic Imaging 244 ' Scanning Acoustic Microscopes Worked Example: Lidar Locust Tracker Requirement Specifications System Hardware Determining the Required Aircraft Speed Laser Power Density on the Ground The power density of the reflected signals back at the laser The Effect of the Sun The Receiver Conclusions References 254 Chapter 7 Signal Propagation The Sensing Environment Attenuation of Electromagnetic Waves Clear Weather Attenuation 259

8 XI Effect of Atmospheric Pressure (air density) Effect of Rain Effect of Fog and Clouds Overall Attenuation Attenuation through Dust and Smoke Attenuation of Radar Signals Attenuation of Laser Signals Effect of atmosphere composition Electromagnetic propagation through solid Refraction of Electromagnetic Waves Acoustics and Vibration Characteristic Impedance (Z) and Sound Pressure Sound Intensity (I) Sound Propagation in Gases Worked Example: Effect of Molecular Weight on Speed of Sound Effect of Temperature and Pressure Sound Propagation in Water Sound Propagation in Solids Attenuation of Sound in Air Attenuation of Sound in Water Reflection and Refraction of Sound Waves normal to the Interface Waves at an angle to the Interface Refraction and Refraction Multipath Effects Mechanism Multipath Lobing Multipath Fading Multipath Tracking Effects on Imaging References 297 Chapter 8 Target and Clutter Characteristics Introduction Target Cross-Section Cross-section and the Equivalent Sphere Cross-section of Real Targets Radar Cross-sections (RCS) RCS of Simple Shapes Flat Plate 302

9 8.4.2 The Sphere Trihedral Reflector Other Simple Calibration Reflectors Radar Cross-section of Complex Targets Aircraft Ships Ground Vehicles Effect of Target Material RCS of Living Creatures Human Beings Birds Insects Fluctuations in Radar Cross-section Temporal Fluctuations Spatial Distribution of Cross-section Radar Stealth Minimizing Detectability Anti-Stealth Technology Target Cross-section in the Infrared Acoustic Target Cross-section Target Composition Target Properties Particulate Targets Underwater Targets Clutter TS of a Sphere TS of Other Shapes Ground Clutter Spatial Variations Temporal Variations Sea Clutter Calculating Surface Clutter Backscatter Calculating Volume Backscatter Rain Dust and Mist Backscatter Sonar Clutter and Reverberation Backscatter Volume Reverberation Worked Example: Orepass Radar Development Requirement Selection of a Sensor 344

10 XIII References 355 Range Resolution 345 Target Characteristics 345 Clutter Characteristics 346 Target Signal-to-Clutter Ratio (SCR) 346 Antenna Size and Radar Frequency 347 Radar Configuration 347 Component Selection Antenna Options Radar Transmitter Receiver Options 349 Signal-to-Noise Ratio 351 Output Signal-to-Noise Ratio 351 Required IF Gain 352 Detection Probability and Pulses Integrated 352 Measurement Update Rate 352 Monitoring Rock Falling Down the Pass 352 Prototype Build and Test 353 Chapter 9 Detection of Signals in Noise 9.1 Receiver Noise Radar Noise Noise Probability Density Functions Infrared Detection and Lidar Noise Thermal Noise Shot Noise Avalanche Noise /f Noise Total Noise Contribution Sonar Noise Thermal Noise Noise from the Sea Effects of Signal-to-noise Ratio Probability of False Alarm Example Probability of Detection Detector Loss Relative to an Ideal System The Matched Filter Coherent Detection Integration of Pulse Trains Detection of Fluctuating Signals Detecting Targets in Clutter

11 XIV Table of Contents 9.8 Constant False Alarm Rate (CFAR) Processors Target Detection Analysis Worked Example: Target Detection with Air Surveillance Radar Determine Receiver Parameters Radar Range Equation Determine the Receiver Noise and SNR Solve for the Detection Range (m) Range Analysis Software Packages Detection Range in Rain Noise Jamming Noise Jamming Example References 388 Chapter 10 Doppler Measurement The Doppler Shift Doppler Shift Derivation Doppler Geometry Targets moving at low velocities (v «c) Targets Moving at High Speed (v < c) Doppler Shift Extraction Direction Discrimination Sideband Filtering Offset Carrier Demodulation In-phase/Quadrature Demodulation Pulsed Doppler Doppler Sensors Continuous Wave Doppler Ultrasound Continuous Wave Doppler Radar Intruder Detection Sports Radar Police Radar Speed Trap Worked Example: Police Radar and Detector Comparison Projectile Tracking Radar Doppler Target Identification Pulsed Doppler Ultrasound Pulsed Doppler Radar Doppler Target Generator 416

12 xv 10.7 Case Study: Estimating the Speed of Radio Controlled Aircraft Background Measured Data References 423 Chapter 11 High Range-Resolution Techniques Classical Modulation Techniques Amplitude Modulation Range Resolution Frequency & Phase Modulation Matched Filter Phase-Coded Pulse Compression Barker Codes Random Codes Optimal Binary Sequences Correlation Binary Correlation Circular Correlation SAW Based Pulse Compression Step Frequency Frequency-modulated continuous-wave Radar Operational Principles Matched Filtering The Ambiguity Function Effect of a Non-Linear Chirp Chirp Linearization Open Loop Techniques Determining the Effectiveness of Linearization Techniques Implementation of Closed-Loop Linearization Direct Digital Synthesis Extraction of Range Information and Range Gating FFT Processing Other Range Gating Methods Problems with FMCW Stretch Interrupted FMCW Disadvantages Optimizing for a Long Range Imaging Application Implementation 458

13 XVI Table of Contents Sidelobes and Weighting for Linear FM Systems High Resolution Radar Systems Industry Automotive Radar Research Radars Worked Example: Brimstone Antitank Missile System Specifications Seeker Specifications (known) Operational procedure Lock-on after launch System Performance (speculated) Target Detection and Identification Radar Front End Antenna and Scanner Signal Processing Signal-to-Clutter Ratio: Clutter Levels Target Levels Signal-to-Clutter Ratio Signal-to-Noise Ratio Target Identification: Doppler Processing Target Identification: Other Techniques Tracking and Guidance References 477 Chapter 12 High Angular-Resolution Techniques Introduction Phased Arrays Advantages of using Phased Arrays Array Synthesis Two Point Array Point Array The General Case The Radiation Pattern Linear Array Radiation pattern: 2D Rectangular Array Beam Steering Active and Passive Arrays Corrections to Improve Range Resolution Array Characteristics Antenna Gain and Beamwidth Matching and Mutual Coupling Thinned arrays Conformal Arrays 495

14 XVII 12.6 Applications Acoustic Array New Generation MMIC Phased Arrays Early Warning Phased Array Radar Sidescan Sonar Operational Principles Hardware Operation and Image Interpretation Signal Processing Worked Example: Performance of the ICT-5202 Transducer Doppler Beam-Sharpening Operational Principles of Synthetic Aperture Range and Cross-range Resolution Unfocused SAR Focused SAR Resolution Comparison Worked Example: Synthetic Aperture Sonar Radar Image Quality Issues Perspective of a Radar Image Image Distortion Stretching Shadowing Speckle SAR on Unmanned Aerial Vehicles TESAR MiniSAR Airborne SAR Capability Space-based SAR Interferometry Magellan Mission to Venus References 537 Chapter 13 Range and Angle Estimation and Tracking Introduction Range Estimation and Tracking Range Gating Principles of a Split-Gate Tracker Range Transfer Function Noise on Split-Gate Trackers Range Tracking Loop Implementation The A-ß Filter 543

15 XVIII Table of Contents The Kaiman Filter Other Tracking Filters Ultrasonic Range Tracker Example Tracking Noise after Filtering Tracking Lag for an Accelerating Target Worked Example: Range Tracker Bandwidth Optimization Range Tracking Systems Lidar Speed Trap Seduction Jamming Angle Measurement Amplitude Thresholding Proximity Detector Example Angle Tracking Principles Scanning Across the Target Null Steering Lobe Switching (Sequential Lobing) Main Disadvantages of Lobe Switching Conical Scan The Squint Angle Optimization Process Measuring the Conscan Antenna Transfer Function Application Main Disadvantages Other considerations Infrared Target Trackers Amplitude Comparison Monopulse Antenna Patterns Generation of Error Signals Comparison between Conscan and Monopulse Angle Tracking Loops Angle Estimation and Tracking Applications Instrument Landing System (ILS) Localizer Transmitter Localizer Receiver Glide Slope Equipment Worked Example: Combined Acoustic and Infrared Tracker Operational Principles of Prototype Theoretical Performance Tracker Implementation Beacon Receiver 582

16 XIX Construction Control Algorithms Angle Track Jamming Triangulation Loran-C References 591 ' Summary of Operation Measurement Process Advantages of Loran-C 590 Chapter 14 Tracking Moving Targets Track While Scan The Coherent Pulsed Tracking Radar Single Channel Detection I/Q Detection Moving Target Indicator (MTI) Blind Speeds Staggered PRF and Blind Speed Limitations to MTI Performance Range-Gated Pulsed Doppler Tracking Coordinate Frames Measurement Frame Tracking and Estimation Frame Antenna Mounts and Servo Systems On-Axis Tracking Crossing Targets and Apparent Acceleration Millimeter Wave Tracking Radar Tracking in Cartesian Space Worked Example: Fire Control Radar Requirements Selection of Polarization Positioner Specifications Radar Horizon Selection of Frequency Adverse Weather Effects Required Single Pulse Signal-to-Noise Ratio Tracking Gate Size Signal-to-Clutter Moving Target Indicator The Pulse Repetition Frequency Search Requirement Integration Gain 630

17 XX Table of Contents Matched Filter Transmitter Power System Configuration Free Space Detection Range Effects of Multipath on Aircraft Detection Detection Threshold and CFAR Transition to Track Target Tracking References 640 Chapter 15 Radio Frequency Identification Tags and Transponders Principle of Operation History Secondary Surveillance Radar Interrogation Equipment Transponder Equipment Operation SSR Issues Sidelobe problems Congestion Radio Frequency Identification (RFID) Systems Electronic Article Surveillance (EAS) Radio Frequency Tags Acousto-Magnetic Tags Microwave Tags (E-tags) Multibit EAS Tags Magnetic Coupled RFID Transponder Systems Operational Principles Electromagnetic Coupled RFID Transponder Systems Other Applications House Arrest Tag Social Issues Technical Challenges Harmonic Radar Battlefield Combat ID System (BCIS) Combat Identification: The Future References 657 Chapter 16 Tomography and 3D Imaging Principle of Operation CT Imaging Image Reconstruction 662

18 XXI What is displayed in CT images Two Dimensional Displays Three Dimensional Displays Magnetic Resonance Imaging (MRI) Nuclear Magnetic Resonance (NMR) Imaging Process Imaging Resolution MRI Images Functional MRI Investigations of Brain Function Positron Emission Tomography Examples of the use of PET Scans D Ultrasound Imaging D Medical Ultrasound D Extension Medical Applications Dangers of Ultrasound Use Ultrasonic Computed Tomography D Sonar Imaging Ground Penetrating Radar D Imaging using GPR Worked Example: Detecting a Ruby Nodule in a Rock Matrix References 693 Index 695