Introduction to Airborne Radar
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Chapter 11 Detection Theory
Chapter 12 HPRF Ranging
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PART I. OVERVIEW OF AIRBORNE RADAR
1. Overview
RADIO DETECTION
Basic Elements of a Radar; Factors Governing Detection Range
DETERMINING TARGET POSITION
Measuring Range; Measuring Direction; Automatic Tracking
EXPLOITING THE DOPPLER EFFECT
Eliminating Clutter; Measuring Velocity
GROUND MAPPING
Characteristics of Radar Maps; Obtaining Fine Resolution; Synthetic Array
Radar
SUMMARY
2. Approaches to Implementation
SIMPLE PULSED RADAR
Functional Elements; The Venerable Magnetron; Common Radar Displays;
Automatic Tracking
ADVANCED MULTIMODE RADAR
Innovations; The Venerable TWT; Digital Processing
3. Representative Applications (significantly updated.)
CIVIL APPLICATIONS
Weather Avoidance; Collision Warning; Wind Shear Detection; Law
Enforcement; Ecological Monitoring; Maritime Uses; High-Resolution Area Mapping; Sounding;
Space Flight
MILITARY APPLICATIONS
Navigation; Early Warning and Sea Surveillance; Ballistic Missile
Detection;
Fighter/Interceptor Mission; Missile Guidance; Air-to-Ground Operations;
Air-to-Surface Naval Applications; Proximity Fuses; Countermeasures;
Stealth
PART II. ESSENTIAL BACKGROUND INFORMATION
4. Radio Waves and Alternating Current Signals
NATURE OF RADIO WAVES
Electric and Magnetic Fields; Electromagnetic Radiation; How an Antenna
Radiates Energy; Visualizing a Wave's Fields
CHARACTERISTICS OF RADIO WAVES
Speed; Duration; Polarization; Intensity; Wavelength; Phase
REFLECTION, REFRACTION, AND DIFFRACTION
5. Key To A Non-mathematical
Understanding of Radar
HOW A PHASOR REPRESENTS A SIGNAL
COMBINING SIGNALS OF DIFFERENT PHASE
COMBINING SIGNALS OF DIFFERENT FREQUENCY
Frequency Translation; Image Frequencies; Creation of Sidebands
RESOLVING SIGNALS INTO I AND Q COMPONENTS
Distinguishing Direction of Doppler Shifts; Differentiating Between
Signals and Images
SUMMARY
6. The Ubiquitous Decibel
WHAT DECIBELS ARE
Origin; Advantages; A Short Course in Logarithms
CONVERTING
Power Ratios to DB; DB to Power Ratios
POWER RATIOS LESS THAN ONE
USING DECIBELS
POWER GAIN IN TERMS OF VOLTAGE
DECIBELS AS ABSOLUTE UNITS
REMEMBERING THE BASIC POWER RATIOS
PART III. RADAR FUNDAMENTALS
7. Choice of Radio Frequency
FREQUENCIES USED FOR RADAR
FREQUENCY BANDS
LASER RADAR FREQUENCIES
INFLUENCE OF FREQUENCY ON:
Physical Size; Maximum Transmitter Power; Antenna Beamwidth; Atmospheric
Attenuation; Ambient Noise; Doppler Considerations
SELECTING THE OPTIMUM FREQUENCY
SUMMARY
8. Directivity and the Antenna Beam
DISTRIBUTION OF ENERGY IN ANGLE
RADIATION PATTERNS
Beamwidth; Gain; Sidelobes; Sidelobe Reduction
ELECTRONIC BEAM STEERING
ANGULAR RESOLUTION
ANGLE MEASUREMENT
Lobing; Monopulse; Beams for Ground Mapping
SUMMARY
9. Pulsed Operation
WHY PULSED TRANSMISSIONCHARACTERISTICS OF THE PULSED WAVEFORM
Carrier Frequency; Interpulse Modulation; Pulse Width; Pulse Repetition
Frequency
POWER
Distinction Between Energy and Power; Peak Power; Average Power
SUMMARY
GENERAL RANGE EQUATION
EQUATION FOR VOLUME SEARCH
DETECTION PROBABILITY
SUMMARY
12. Pulse Delay Ranging
BASIC TECHNIQUE IN:
Simple Analog Radars; Sophisticated Analog Radars; Digital Systems
RANGE AMBIGUITIES
Nature; Eliminating Ambiguous Return; Resolving Ambiguities
GHOSTS
What They Are; Eliminating Them
HOW MANY PRFS?
SINGLE TARGET TRACKING
SUMMARY
13. Pulse Compression
LINEAR FREQUENCY MODULATION (CHIRP)
Concept; Range Sidelobes; Stretch Radar Decoding; Pulse Compression Ratio
BINARY PHASE MODULATION
Concept; Barker Codes; Chained Complementary Codes
POLYPHASE CODES
SUMMARY
14. FM Ranging
BASIC PRINCIPLE
ACCOUNTING FOR DOPPLER SHIFTS
Constant Frequency Segment; Alternative Two-Slope Cycle
GHOSTS
Why Ghosts; Identifying Ghosts; Three Simultaneous Targets
PERFORMANCE
SUMMARY
PART IV. PULSE DOPPLER RADAR
15. The Doppler Effect
WHAT THE EFFECT IS
A Crowding, or Spreading, of Wavefronts; A Continuous Phase Shift;
Equation Derived
DOPPLER FREQUENCIES OF:
Aircraft; Ground Return; Target Seen By A Semiactive Missile
SUMMARY
16. Spectrum Of A Pulsed Signal
BANDWIDTH
CW Signal; Single Pulse; Train of Independent Pulses
COHERENCE
How Achieved; Effect on Spectrum of a Pulse Train
SPECTRAL LINE WIDTH
Relationship to Length of Pulse Train; Equivalence to Spectrum of Single
Long Pulse
SUMMARY
17. Mysteries of The Pulsed Spectrum Unveiled
CRUX OF THE MATTER
Spectrum Defined; Response of a Lossless Filter; Frequency Defined
EXPLANATION IN TERMS OF FOURIER SERIES
Fourier Series for a Pulsed Signal; Spectrum of Pulse-Modulated Carrier;
Spectrum of a Single Pulse; Spectrum Line Width
EXPLANATION IN TERMS OF FILTER RESPONSE
Single Pulse; Coherent Pulse Train; Repetition of Spectral Lines
MATHEMATICAL EXPLANATION
Fourier Transform Derived; Negative Frequencies; Power Spectrum Energy
Distribution
SUMMARY
18. Sensing Doppler Frequencies
THE DOPPLER FILTER BANK
Bandwidth of the Filters; Passband of the Bank
ANALOG FILTERS
Analogy to a Pendulurn; Practical Filters
DIGITAL FILTERING
Translation to Video Frequencles; Sampling the Video Signals;
Analog-to-Digital Conversion; Forming the Filters
PROVIDING ADEQUATE DYNAMIC RANGE
Sources of Spurious Signals; Avoiding Saturation; Dealing With
Quantization Noise
SUMMARY
19. How Digital Filters Work
INPUTS TO THE FILTER
Viewed on a Range Trace; Represented by Phasors
THE FILTER
The DFT Derived; Approximating The Vector Sum
IMPLEMENTING THE DFT
Single Channel; Multiple Range Gates; Dual Channel
SIDELOBE REDUCTION
FILTERING ACTUAL SIGNALS
SUMMARY
20. The Digital Filter Bank & The FFT
BASIC CONCEPT
A REPRESENTATIVE FFT
Required Phase Rotations; Processing Flow Diagram; Reduction In
Computations; Rotating the Phases; Identifying the Filter Outputs; Forming the Magnitudes
FFTS FOR FILTER BANKS OF ANY SIZE
Determining the Required Phase Rotations; The FFT Butterfly
RULES OF THUMB FOR ESTIMATING NUMBER OF COMPUTATIONS
SUMMARY
21. Measuring Range Rate
METHODS OF MEASUREMENT
Range Differentiation; Sensing Doppler Frequency
POTENTIAL DOPPLER AMBIGUITIES
RESOLVING AMBIGUITIES
SUMMARY
PART V. THE PROBLEM OF GROUND CLUTTER
22. Sources & Spectra of Ground Return
ARNPLITUDE OF THE RETURN
Governing Factors; Backscattering Coefficient
CHARACTERISTICS AND SPECTRA OF:
Mainlobe Return; Sidelobe Clutter; Altitude Return
CLUTTER AND TARGET FREQUENCIES COMPARED
RETURN FROM OBJECTS ON THE TERRAIN
SUMMARY
23. Effect of Range and Doppler Ambiguities on Ground Clutter
DISPERSED NATURE OF CLUTTER
RANGE PROFILE
Return From Ranges Separated by Ru; Range Zones; Zones Superimposed
DOPPLER PROFILE
Repetitions of Profile at Intervals of fr; Repetitions Superimposed
SUMMARY
24. Separating Ground Moving Target From Clutter(
THE PROBLEM
CLASSICAL DPCA
NOTCHING TECHNIQUE
COMBINED CLASSICAL DPCA AND NOTCHING
ANGLE MEASUREMENT
SUMMARY
PART VI. AIR-TO-AIR OPERATION
25. The Crucial Choice of PRF
PRIMARY CONSIDERATIONS
Range Ambiguities; Doppler Arnbiguities
THREE CATEGORIES OF PRF DEFINED
RELATIVE MERITS
Low PRF; Medium PRF; High PRF
SUMMARY
26. Low PRF Operation
SEPARATING TARGETS FROM CLUTTER
SENSITIVITY TIME CONTROL
SIGNAL PROCESSING (DOPPLER RADAR)
Basic Mechanization; What a Range Bin Is; How a Clutter Canceler Works;
Setting the Detection Threshold; Tracking Mainlobe Clutter
LESS SOPHISTICATED SIGNAL PROCESSING
ADVANTAGES AND LIMITATIONS
GETTING AROUND THE LIMITATIONS
Doppler Blind Zones; Multiple-Time-Around Echoes; Low Duty Factor; Moving
Targets on the Ground
SUMMARY
27. Medium PRF Operation
SEPARATING TARGETS FROM CLUTTER
Mainlobe Sidelobe
SIGNAL PROCESSING
Range Gating & Filtering; Digital AGC; Setting Detection; Thresholds
Special Considerations; Rejecting GMTs; Eliminating Blind Zones; Minimizing Sidelobe
Clutter; Rejecting Ground Targets of Large Radar Cross Section
SUMMARY
28. High PRF Operation
ISOLATING TARGET RETURN
Rejecting Strong Clutter; Providing Doppler Resolution; Range Gating
SIGNAL PROCESSING
Analog; Digital
RANGING
SPECIAL CONSIDERATIONS
The Problem of Eclipsing; Improving Tail Aspect Performance; Illuminating
Targets for Missiles
SUMMARY
29. Automatic Tracking
SINGLE-TARGET TRACK
Angle Tracking Loop; Range Tracking Loop; Velocity Tracking Loop
TRACK-WHILE-SCAN
SUMMARY
PART VII. HIGH RESOLUTION GROUND MAPPING AND IMAGING
30. Meeting High Resolution Ground Mapping Requirements
HOW RESOLUTION IS DEFINED
FACTORS INFLUENCING CHOICE OF CELL SIZE
Size of Objects to be Resolved; Cost; Amount of Processing Required; Task
of Interpreting the Maps
ACHIEVING FINE RESOLUTION
In Range In Azimuth
SYNTHETIC ARRAY RADAR (SAR)
Optical Processing; Digital Processing
SUMMARY
31. Principles of Synthetic Array Radar
BASIC CONCEPT
A RUDIMENTARY ARRAY
Signal Processing Required; Limitation of Unfocused Arrays
THE FOCUSED ARRAY
How Focusing Is Done; Signal Processing Required; Resolution Obtained
DOPPLER PROCESSING
Doppler Frequency Versus Azimuth; Implementation; Similarity to Stretch
Processing; Reduction In Computing Load; Correspondence to Antenna Concepts
SUMMARY
32. SAR Design Considerations & Operating Modes
CRITICAL DESIGN CONSIDERATIONS
Range and Doppler Ambiguities; Grating Lobes; Minimizing Sidelobes; Motion
Compensation; Uncompensated Phase Errors
OPERATIONAL MODES
Squinted Array; Display of Moving Targets; Spotlight Mode; Multilook
Capability; Doppler Beam Sharpening
INVERSE SAR (ISAR)
PART VIII ELECTRONIC WARFARE (EW) (
ALL NEW CHAPTERS)
33. Electronic Countermeasures (ECM)
CHAFF
NOISE JAMMING
Mechanization; Effectiveness; Cooperatively Blinked; Jamming More Than One
Radar
FALSE TARGETS
GATE STEALING DECEPTION
Range Gate Stealers; Velocity Gate Stealers; Coordinated Range/Velocity
Gate Stealing
ANGLE DECEPTION
Terrain Bounce; Crosseye; Cross Polarization; Double Cross
RADAR DECOYS
FUTURE TRENDS
SUMMARY
34. Electronic Counter Countermeasures (ECCM)
CONVENTIONAL COUNTERS TO NOISE JAMMING
Frequency Agility and Its Limitations; Detection & Angle Tracking on
Jamming; Passive Ranging; Clutter-Reduciton Features that Reduce Vulnerability to Noise
Jamming
CONVENTIONAL COUNTERS TO DECEPTION ECM
Countering Range Gate Stealers; Countering Velocity Gate Stealers;
Countering Deception of Lobing Systems; Countering Terrain Bounce; Countering Crosseye and
Crosspol; Countering Jamming in Surface-Based Radars & SAMs
ADVANCED ECCM DEVELOPMENTS
Sidelobe Jamming Cancellation; Mainlobe Jamming Cancellation;
Exceptionally Broad RF Bandwidths
SENSOR FUSION
Offensive ECCM; Application of Artificial Intelligence to ECCM
THE MOST EFFECTIVE ECCM OF ALL
SUMMARY
35. EW Intelligence Functions
BASIC TYPES OF ECM
Chaff; Noise Jamming; Deception; ECM
OFFENSIVE ECM
Standoff Jamming; Escort Jamming; Mutual Support Jamming
DEFENSIVE ECM
BASIC APPROACHES TO ECCM
Countering Chaff; Countering Noise Jamming; Countering Deception ECM
AN ENDLESS LOOP
ELECTRONIC SUPPORT MEASURES (ESM)
Detecting RF Emissions; Extracting Key Signal Parameters; Identifying
Sources
RADAR WARNING RECEIVER (RWR)
SUMMARY
PART IX. ADVANCED CONCEPTS
36. Electronically Steered Array Antennas (ESAs)
BASIC CONCEPTS
TYPES OF ARRAYS
Passive ESA; Active ESA
ADVANTAGES COMMON TO BOTH TYPES
Facilitating RCS Reduction; Extreme Beam Agility; High Reliability
OTHER ADVANTAGES OF ACTIVE ESAS
KEY LIMITATIONS AND THEIR CIRCUMVENTION
Achieving a Broad Field of Regard; Beam Stabilization
SUMMARY
37. ESA Design
FACTORS COMMON TO BOTH TYPES OF ESAS
Avoiding Grating Lobes; Avoiding Bragg Lobes; Choice of Lattice Pattern
DESIGN OF PASSIVE ESAS
Phase Shifters; Feed Type; Transmission Lines
DESIGN OF ACTIVE ESAS
Chip Set; Power Output; Transmitter Noise Limitations; Receiver Noise
Figure; Array Physical Design
SUMMARY
38. Antenna RCS Reduction
SOURCES OF REFLECTIONS FROM A PLANAR ARRAY
REDUCING AND CONTROLLING ANTENNA RCS
Rendering Structural Mode Reflections Harmless; Minimizing Antenna Mode
Reflections; Minimizing Edge Diffraction; Minimizing Random Scattering
AVOIDING BRAGG LOBES
VALIDATING THE PREDICTED RCS
SUMMARY
39. Advanced Radar Techniques
APPROACHES TO MULTIPLE FREQUENCY OPERATION
Simultaneous Frequency Agile Radar (SIMFAR); STAR
SMALL TARGET DETECTION
Refinement of Conventional Radar Features; Long Coherent Integration
Times; Sequential Detection
BISTATIC TARGET DETECTION
Cooperative Detection; Noncooperative Detection
PHOTONIC FEEDS FOR ACTIVE ESAS
Basic Concept; Advantages
ADVANCED WAVEFORMS
Range-Gated High PRF; Pulse Burst; Monopulse Doppler; Coherent Low PRF ^
SUMMARY
40. Advanced Waveforms & Mode Control
RANGE-GATED HIGH PRF
PULSE BURST
MONOPULSE DOPPLER
COHERENT LOW PRF
MODE CONTROL
SUMMARY
41. Low Probability of Intercept (LPI)
GENERIC INTERCEPT RECEIVERS
RWR; ECM System; Bound Based Systems; ARM
OPERATIONAL STRATEGIES
DESIGN STRATEGIES
TRADE SIGNAL INTEGRATION FOR REDUCED PEAK POWER
Trade Bandwidth for Reduced Peak Power; Trade Antenna Gain for Reduced
Peak Power; Multiple Beams on Different Frequencies; Random Waveform Parameters; Mimicking
Enemy Waveforms
THE COST OF LPI
POSSIBLE FUTURE TRENDS
SUMMARY
42. Advanced Processing Architecture
PARALLEL PROCESSING
DISTRIBUTED PROCESSING
Pipeline Processing
HIGH THROUGHPUT DENSITY
Types of VLSls; Gate Arrays
MODULAR DESIGN
One Approach to Clustering; Another Clustering Approach; Advantages
FAULT TOLERANCE
INTEGRATED PROCESSING
F-22 Example; UAV Example; Providing Data Security
ADVANCED DEVELOPMENTS
Higher Clock Rates; Higher Density Gate Array
DENSER PACKAGING
Advanced Architectures
SUMMARY
PART X APPLICATIONS
43. Representative Multimode Radar Systems
APG 63 RADAR FOR F-15
Primary Modes of Operation; Basic Functional Elements; Low PRF Signal
Processing; Medium PRF Signal Processing
APG 73 RADAR FOR F/A-18 E/F
Primary Modes of Operation; Basic Functional Elements; Low PRF Signal
Processing; Signal Processing
[Others being added up to the last minute]
APPENDICES
Rules of Thumb; Reference Data
List of Symbols
Recommendations for Further Reading
Index
Index to Blue Panels Copyright ©1997 SciTech Publishing, Inc.
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