Sensors for Ranging and Imaging (Electromagnetic Waves)

Title
Copyright
Contents
About the author
Acknowledgements
Chapter 1 Introduction to sensing
	1.1 Introduction
		1.1.1 Active sensors
		1.1.2 Passive sensors
	1.2 A brief history of sensing
		1.2.1 Sonar
		1.2.2 Radar
		1.2.3 Lidar
	1.3 Passive infrared sensing
	1.4 Sensor systems
	1.5 Frequency band allocations for the electromagnetic spectrum
	1.6 Frequency band allocations for the acoustic spectrum
	References
Chapter 2 Signal processing and modulation
	2.1 The nature of electronic signals
	2.2 Noise
		2.2.1 Thermal noise
		2.2.2 Shot noise
		2.2.3 1/f Noise
		2.2.4 Avalanche noise
	2.3 Generating analogue signals
		2.3.1 Generating digital signals
	2.4 Signals and noise in the frequency domain
		2.4.1 The Fourier series
	2.5 Analogue signal processing
		2.5.1 Amplifiers
		2.5.2 Practical considerations
	2.6 Analogue filters
		2.6.1 Low-pass filter
		2.6.2 High-pass filters
		2.6.3 Bandpass filters
		2.6.4 Notch and band-reject filters
		2.6.5 Active filter implementation
		2.6.6 Other analogue circuits
	2.7 Digital signal processing
		2.7.1 Signal aliasing
		2.7.2 Digital filters
	2.8 Analogue modulation and demodulation
		2.8.1 Amplitude modulation
	2.9 Frequency modulation
	2.10 Linear frequency modulation
	2.11 Pulse-coded modulation techniques
		2.11.1 Pulse amplitude modulation
		2.11.2 Binary frequency shift keying
		2.11.3 Phase-shift keying
		2.11.4 Split phase codes
		2.11.5 Stepped frequency modulation
	2.12 Convolution
		2.12.1 Linear time-invariant systems
		2.12.2 The convolution sum
		2.12.3 Worked example: pulsed radar echo amplitude
	References
Chapter 3 IR radiometers and image intensifiers
	3.1 Introduction
	3.2 Thermal emission
		3.2.1 Blackbody radiation
		3.2.2 The Planck function
		3.2.3 Properties of the Planck function
		3.2.4 Confirmation of Stefan__amp__#8211;Boltzmann and Rayleigh__amp__#8211;Jean laws
	3.3 Emissivity and reflectivity
		3.3.1 Worked example: blackbody radiation from human body
	3.4 Detecting thermal radiation
		3.4.1 External photoeffect
		3.4.2 Internal photoeffect
		3.4.3 Heating
	3.5 Performance criteria for detectors
		3.5.1 Responsivity
		3.5.2 Noise-equivalent power
		3.5.3 Detectivity and specific detectivity
	3.6 Noise processes and effects
	3.7 Applications
		3.7.1 Passive ultraviolet sensor (external photoeffect)
		3.7.2 Radiation thermometer (internal photoeffect: thermopile)
		3.7.3 Passive infrared sensor (internal photoeffect: pyroelectric)
		3.7.4 Crookes radiometer
	3.8 Introduction to thermal imaging systems
		3.8.1 Scattering and absorption
		3.8.2 Scanning mechanisms and arrays
		3.8.3 Micro-bolometer arrays
		3.8.4 Key optical parameters
	3.9 Performance measures for infrared imagers
		3.9.1 Detector field of view
		3.9.2 Spatial frequency
		3.9.3 Signal-to-noise ratio for a point target
		3.9.4 Worked example: IRST system snr
		3.9.5 Signal-to-noise ratio for a target in ground clutter
		3.9.6 Noise-equivalent temperature difference
		3.9.7 Example
		3.9.8 The minimum resolvable temperature difference
	3.10 Target detection and recognition
		3.10.1 Example of FLIR detection
	3.11 Thermal imaging applications
	3.12 Image intensifiers
		3.12.1 First-generation tubes
		3.12.2 Second-generation tubes
		3.12.3 Third-generation tubes
		3.12.4 Spectral characteristics of the scene
		3.12.5 Time gating microchannel plates
	References
Chapter 4 Millimetre-wave radiometers
	4.1 Antenna power temperature correspondence
		4.1.1 Example of power received from a blackbody
	4.2 Brightness temperature
	4.3 Apparent temperature
	4.4 Atmospheric effects
		4.4.1 Attenuation
		4.4.2 Downwelling radiation
		4.4.3 Upwelling radiation
	4.5 Terrain brightness
	4.6 Worked example: space-based radiometer
		4.6.1 Temperature contrast
	4.7 Antenna considerations
		4.7.1 Beamwidth
		4.7.2 Efficiency
		4.7.3 Fill ratio
	4.8 Receiver considerations
		4.8.1 Mixer implementations for microwave receivers
		4.8.2 Noise figure
	4.9 The system noise temperature
	4.10 Radiometer temperature sensitivity
	4.11 Radiometer implementation
		4.11.1 Total power radiometer
		4.11.2 Dicke radiometer
		4.11.3 Performance comparison between radiometer types
	4.12 Intermediate frequency and video gain requirements
		4.12.1 Direct detection radiometers
	4.13 Worked example: anti-tank sub-munition sensor design
		4.13.1 Radiometer implementation
		4.13.2 Receiver noise temperature
		4.13.3 Minimum detectable temperature difference
	4.14 Radiometric imaging
		4.14.1 Image processing
	4.15 Applications
		4.15.1 Airborne scanned millimetre-wave radiometer
		4.15.2 Scanning multi-channel microwave radiometer
		4.15.3 Ground-based millimetre-wave radiometers
		4.15.4 Radio astronomy
	References
Chapter 5 Active ranging sensors
	5.1 Overview
	5.2 Triangulation
	5.3 Pulsed time-of-flight operation
		5.3.1 Sensor requirements
		5.3.2 Speed of propagation
		5.3.3 The antenna
		5.3.4 The transmitter
		5.3.5 The receiver
	5.4 Using pulsed time of flight
		5.4.1 Timing discriminators
		5.4.2 Pulse integration
		5.4.3 Time transformation
	5.5 Other methods of measuring range
		5.5.1 Ranging using an unmodulated carrier
		5.5.2 Ranging using a modulated carrier
		5.5.3 Tellurometer example
	5.6 The radar range equation
		5.6.1 Derivation
		5.6.2 The dB form
		5.6.3 Worked example: radar detection calculation
		5.6.4 Receiver noise
		5.6.5 Determining the required signal level
		5.6.6 Pulse integration and the probability of detection
	5.7 The acoustic range equation
		5.7.1 Example of using the acoustic range equation
	5.8 TOF measurement considerations
	5.9 Range measurement radar for a cruise missile
	References
Chapter 6 Active imaging sensors
	6.1 Imaging techniques
	6.2 Range-gate limited 2D image construction
	6.3 Beamwidth-limited 3D image construction
		6.3.1 Push-broom scanning
		6.3.2 Mechanical scanning
	6.4 The lidar range equation
	6.5 Lidar system performance
		6.5.1 Direct detection
		6.5.2 Heterodyne detection
		6.5.3 Signal-to-noise ratio and detection probability
		6.5.4 Worked example: lidar reflection from the moon
	6.6 Digital terrain models
		6.6.1 Surface models
		6.6.2 Digital landscapes
		6.6.3 Thematic visualisation
	6.7 Airborne lidar hydrography
		6.7.1 Laser airborne depth sounder
		6.7.2 Photoacoustic airborne sonar system
	6.8 3D imaging
		6.8.1 Scanned radar systems
		6.8.2 MIMO systems
		6.8.3 Focused beam radar imaging
		6.8.4 Line-scan lidar imaging
		6.8.5 Lidar for autonomous vehicles
		6.8.6 Unconventional scanning mechanisms
		6.8.7 Jigsaw __amp__#8211; foliage-penetrating lidar
	6.9 Acoustic imaging
		6.9.1 Scanning acoustic microscopes
	6.10 Worked example: lidar locust tracker
		6.10.1 Requirement
		6.10.2 Specifications
		6.10.3 System hardware
		6.10.4 Determining the required aircraft speed
		6.10.5 Laser power density on the ground
		6.10.6 The power density of the reflected signals back at the laser
		6.10.7 The effect of the sun
		6.10.8 The receiver
		6.10.9 Conclusions
	References
Chapter 7 Signal propagation
	7.1 The sensing environment
	7.2 Attenuation of electromagnetic waves
		7.2.1 Clear weather attenuation
		7.2.2 Effect of atmospheric pressure (air density)
		7.2.3 Effect of rain
		7.2.4 Effect of fog and clouds
		7.2.5 Overall attenuation
		7.2.6 Attenuation through dust and smoke
		7.2.7 Effect of atmosphere composition
		7.2.8 Electromagnetic propagation through solid materials
	7.3 Refraction of electromagnetic waves
	7.4 Acoustics and vibration
		7.4.1 Characteristic impedance (Z) and sound pressure
		7.4.2 Sound intensity (I)
		7.4.3 Sound propagation in gases
		7.4.4 Sound propagation in water
		7.4.5 Sound propagation in solids
		7.4.6 Attenuation of sound in air
	7.5 Attenuation of sound in water
	7.6 Reflection and refraction of sound
		7.6.1 Waves normal to the interface
		7.6.2 Waves at an angle to the interface
		7.6.3 Propagation paths
	7.7 Multipath effects
		7.7.1 Mechanism
		7.7.2 Multipath lobing
		7.7.3 Multipath fading
		7.7.4 Multipath tracking
		7.7.5 Multipath experiment with ultrasound
		7.7.6 Multipath effects on imaging
	References
Chapter 8 Target and clutter characteristics
	8.1 Introduction
	8.2 Definition of target cross-section
		8.2.1 Cross-section and the equivalent sphere
		8.2.2 Cross-section of real targets
	8.3 Radar cross-sections of man made objects
		8.3.1 Simple shapes
		8.3.2 Radar cross-section of complex targets
	8.4 Effect of target material on RCS
	8.5 RCS of living creatures
		8.5.1 Human beings
		8.5.2 Birds
		8.5.3 Insects
	8.6 Fluctuations in radar cross-section
		8.6.1 Temporal fluctuations
		8.6.2 Spatial distribution of cross-section
	8.7 Radar stealth
		8.7.1 Minimising detectability
		8.7.2 Anti-stealth technology
	8.8 Target cross-section in the infrared
	8.9 Acoustic target cross-section
		8.9.1 Target composition
		8.9.2 Target properties
		8.9.3 Particulate targets
		8.9.4 Underwater targets
	8.10 Clutter cross-section
		8.10.1 Ground clutter
		8.10.2 Sea clutter
	8.11 Surface clutter backscatter
	8.12 Calculating volume backscatter
		8.12.1 Rain
		8.12.2 Dust and mist
		8.12.3 Chaff
	8.13 Underwater Clutter
		8.13.1 Backscatter
		8.13.2 Volume reverberation
	8.14 Worked example: orepass radar development
		8.14.1 Requirement
		8.14.2 Selection of a sensor
		8.14.3 Range resolution
		8.14.4 Target characteristics
		8.14.5 Clutter characteristics
		8.14.6 Target signal-to-clutter ratio (SCR)
		8.14.7 Antenna size and radar frequency
		8.14.8 Radar configuration
		8.14.9 Component selection
		8.14.10 Signal-to-noise ratio
		8.14.11 Measurement update rate
		8.14.12 Monitoring rock falling down the pass
		8.14.13 Prototype build and test
	References
Chapter 9 Detection of signals in noise
	9.1 Introduction
	9.2 Radar noise
		9.2.1 Noise probability density functions
	9.3 Infrared detection and lidar noise
		9.3.1 Thermal noise
		9.3.2 Shot noise
		9.3.3 Avalanche noise
		9.3.4 1/f noise
		9.3.5 Total noise contribution
	9.4 Sonar noise
		9.4.1 Thermal noise
		9.4.2 Noise from the sea
	9.5 Effects of signal-to-noise ratio
		9.5.1 Probability of false alarm
		9.5.2 Probability of detection
		9.5.3 Detector loss relative to an ideal system
	9.6 The matched filter
	9.7 Coherent detection
	9.8 Integration of pulse trains
	9.9 Detection of fluctuating signals
	9.10 Detecting targets in clutter
	9.11 Constant false alarm rate (CFAR) processors
	9.12 Target detection analysis
		9.12.1 Worked example: target detection with an air surveillance radar
		9.12.2 Range analysis software packages
		9.12.3 Detection range in rain
	9.13 Noise jamming
		9.13.1 Noise jamming example
	References
Chapter 10 Doppler measurement
	10.1 The Doppler shift
		10.1.1 Doppler shift derivation
	10.2 Doppler geometry
		10.2.1 Targets moving at low velocities (v__amp__#8810;c)
		10.2.2 Targets moving at high speed (v __amp__lt; c)
	10.3 Doppler shift extraction
		10.3.1 Direction discrimination
	10.4 Pulsed Doppler
	10.5 Doppler sensors
		10.5.1 Continuous wave Doppler ultrasound
		10.5.2 Continuous wave Doppler radar
		10.5.3 Pulsed Doppler ultrasound
		10.5.4 Pulsed Doppler radar
	10.6 Doppler target generators
		10.6.1 Spinning reflectors
		10.6.2 Electronic targets
		10.6.3 Piezoelectric target
	10.7 Case study: estimating the speed of radio-controlled aircraft
		10.7.1 Background
		10.7.2 Measured data
	References
Chapter 11 High-range-resolution techniques
	11.1 Classical modulation techniques
	11.2 Amplitude modulation
		11.2.1 Range resolution
	11.3 Frequency and phase modulation
		11.3.1 Matched filter
	11.4 Phase-coded pulse compression
		11.4.1 Barker codes
		11.4.2 Random codes
		11.4.3 Correlation
	11.5 SAW-based pulse compression
	11.6 Step frequency
	11.7 Frequency-modulated continuous-wave radar
		11.7.1 Operational principles
		11.7.2 Matched filtering
		11.7.3 The ambiguity function
		11.7.4 Effect of a non-linear chirp
		11.7.5 Chirp linearisation
		11.7.6 Extraction of range information and range gating
		11.7.7 Problems with FMCW
	11.8 Stretch
	11.9 Interrupted FMCW
		11.9.1 Disadvantages
		11.9.2 Optimising for a long-range imaging application
		11.9.3 Implementation
	11.10 Side lobes and weighting for linear FM systems
	11.11 Transmitter leakage and phase noise in FMCW radars
	11.12 High-resolution radar systems
		11.12.1 Industry
		11.12.2 Automotive radar
		11.12.3 Research radars
	11.13 Worked example: Brimstone antitank missile
		11.13.1 System specifications
		11.13.2 Seeker specifications (known)
		11.13.3 Operational procedure __amp__#8211; Lock-on after launch
		11.13.4 System performance (speculated)
		11.13.5 Dual-look target confirmation
		11.13.6 Transition to track
		11.13.7 Tracking and guidance
		11.13.8 Dual-mode Brimstone
	References
Chapter 12 High angular-resolution techniques
	12.1 Introduction
	12.2 Phased arrays
		12.2.1 Advantages of using phased arrays
		12.2.2 Using metamaterials to improve antenna performance
		12.2.3 Array synthesis
		12.2.4 Two-point array
		12.2.5 Four-point array
		12.2.6 The general case
	12.3 The radiation pattern
		12.3.1 Linear array
		12.3.2 Radiation pattern: 2D rectangular array
	12.4 Beam steering
		12.4.1 Active and passive arrays
		12.4.2 Corrections to improve range resolution
	12.5 Array characteristics
		12.5.1 Antenna gain and beamwidth
		12.5.2 Matching and mutual coupling
		12.5.3 Thinned arrays
		12.5.4 Conformal arrays
	12.6 Applications
		12.6.1 Acoustic array
		12.6.2 MMIC phased arrays
		12.6.3 Early warning phased array radar
	12.7 Side-scan sonar
		12.7.1 Operational principles
		12.7.2 Hardware
		12.7.3 Operation and image interpretation
		12.7.4 Signal processing
	12.8 Worked example: performance of the ICT-5202 transducer
	12.9 Doppler beam-sharpening
		12.9.1 Overview
		12.9.2 DBS analysis
		12.9.3 Image formation
		12.9.4 Worked example: DBS sonar
	12.10 Operational principles of synthetic aperture
	12.11 Range and cross-range resolution
		12.11.1 Unfocused SAR
		12.11.2 Focused SAR
		12.11.3 Resolution comparison
	12.12 Worked example: synthetic-aperture sonar
	12.13 Radar-image-quality issues
		12.13.1 Perspective of a radar image
		12.13.2 Image distortion
		12.13.3 Speckle
	12.14 SAR on unmanned aerial vehicles
		12.14.1 Tactical Endurance Synthetic-Aperture Radar
		12.14.2 MiniSAR
		12.14.3 Other UAV-based SAR systems
	12.15 Airborne SAR capability
	12.16 Space-based SAR
		12.16.1 Interferometric SAR
	12.17 Magellan Mission to Venus
	References
Chapter 13 Range and angle estimation and tracking
	13.1 Introduction
	13.2 Range estimation and tracking
		13.2.1 Range gating
	13.3 Principles of a split-gate tracker
		13.3.1 Range transfer function
		13.3.2 Noise on split-gate trackers
	13.4 Range tracking loop implementation
		13.4.1 The __amp__#945;__amp__#8211;__amp__#946; filter
		13.4.2 The __amp__#945;__amp__#8211;__amp__#946;__amp__#8211;__amp__#947; filter
		13.4.3 The Kalman filter
		13.4.4 Other fixed gain tracking filters
	13.5 Ultrasonic range tracker example
	13.6 Tracking noise after filtering
	13.7 Tracking lag for an accelerating target
	13.8 Worked example: range tracker bandwidth optimisation
	13.9 Range tracking systems
		13.9.1 Lidar speed trap
	13.10 Seduction jamming
	13.11 Angle measurement
		13.11.1 Amplitude thresholding
		13.11.2 Proximity detector example
	13.12 Angle tracking principles
		13.12.1 Scanning across the target
		13.12.2 Null steering
	13.13 Lobe switching (sequential lobing)
		13.13.1 Main disadvantages of lobe switching
	13.14 Conical scan
		13.14.1 The squint angle optimisation process
		13.14.2 Measuring the conscan antenna transfer function
		13.14.3 Application
		13.14.4 Main disadvantages
		13.14.5 Other considerations
	13.15 Infrared target trackers
	13.16 Amplitude comparison monopulse
		13.16.1 Antenna patterns
		13.16.2 Generation of error signals for a microwave radar
		13.16.3 Ultrasound sonar beacon tracker example
		13.16.4 Classical monopulse radar
		13.16.5 Monopulse tracking using phased array
	13.17 Comparison between conscan and monopulse
	13.18 Angle tracking loops
		13.18.1 Motor control
		13.18.2 Tracking error
	13.19 Angle estimation and tracking applications
		13.19.1 Instrument landing system
	13.20 Worked example: combined acoustic and infrared tracker
		13.20.1 Operational principles of prototype
		13.20.2 Theoretical performance
		13.20.3 Tracker implementation
		13.20.4 Construction
		13.20.5 Control algorithms
	13.21 Angle track jamming
	13.22 Triangulation and trilateration
		13.22.1 Loran-C
	References
Chapter 14 Tracking moving targets
	14.1 Track while scan
	14.2 The coherent pulsed tracking radar
		14.2.1 Single-channel detection
		14.2.2 I/Q detection
		14.2.3 Moving target indicator
	14.3 Limitations to MTI performance
	14.4 Range-gated pulsed Doppler tracking
	14.5 Coordinate frames
		14.5.1 Measurement frame
		14.5.2 Tracking and estimation frame
	14.6 Antenna mounts and servo systems
	14.7 On-axis tracking
		14.7.1 Crossing targets and apparent acceleration
	14.8 Millimetre-wave tracking radar
	14.9 Tracking in Cartesian space
	14.10 Combining radar and optronic tracking
	14.11 Worked example: fire control radar
		14.11.1 Requirements
		14.11.2 Selection of polarisation
		14.11.3 Positioner specifications
		14.11.4 Radar horizon
		14.11.5 Selection of frequency
		14.11.6 Adverse weather effects
		14.11.7 Required single-pulse signal-to-noise ratio
		14.11.8 Tracking gate size
		14.11.9 Signal-to-clutter
		14.11.10 Moving target indicator
		14.11.11 The pulse repetition frequency
		14.11.12 Search requirement
		14.11.13 Integration gain
		14.11.14 Matched filter
		14.11.15 Transmitter power
		14.11.16 System configuration
		14.11.17 Free-space detection range
		14.11.18 Effects of multipath on aircraft detection
		14.11.19 Detection threshold and CFAR
		14.11.20 Transition to track
		14.11.21 Target tracking
	References
Chapter 15 RFID tags and transponders
	15.1 Principle of operation
	15.2 History
	15.3 Secondary surveillance radar
		15.3.1 Interrogation equipment
		15.3.2 Transponder equipment
		15.3.3 Operation
		15.3.4 SSR issues
	15.4 Automatic Dependent Surveillance__amp__#8211;Broadcast
		15.4.1 Data format
	15.5 AIS transponders
	15.6 Radio-frequency identification (RFID) systems
		15.6.1 Electronic article surveillance
		15.6.2 Multibit EAS tags
		15.6.3 Magnetic coupled RFID transponder systems
		15.6.4 Electromagnetic coupled RFID transponder systems
	15.7 Other applications
		15.7.1 House arrest tag
		15.7.2 Animal tracking
		15.7.3 Near-field communications and proximity cards
	15.8 Social issues of RFID
	15.9 Technical challenges
	15.10 Harmonic radar
	15.11 Passive reflected power modulation
	15.12 Battlefield combat ID system
		15.12.1 Combat identification: the future
	15.13 Indoor localisation
	References
Chapter 16 Tomography and 3D imaging
	16.1 Principle of operation
	16.2 CT imaging
		16.2.1 Image reconstruction
		16.2.2 What is displayed in CT images
		16.2.3 Two-dimensional displays
		16.2.4 Three-dimensional displays
	16.3 Magnetic resonance imaging
		16.3.1 Nuclear magnetic resonance
		16.3.2 Imaging process
		16.3.3 Imaging resolution
	16.4 Magnetic resonance images
		16.4.1 Contrast enhancement
		16.4.2 DICOM files
	16.5 Functional MRI investigations of brain function
	16.6 Positron emission tomography
		16.6.1 Examples of the use of PET scans
	16.7 3D ultrasound imaging
		16.7.1 2D medical ultrasound
	16.8 3D extension
		16.8.1 Ultrasonic computed tomography
	16.9 Pocket ultrasound
	16.10 Other ultrasound imaging modalities
		16.10.1 Tissue harmonic imaging
		16.10.2 Colour flow mapping
		16.10.3 Shear wave elastography
	16.11 Sonar imaging in 3D
	16.12 Ground-penetrating radar
		16.12.1 3D imaging using GPR
	16.13 Worked example: detecting a ruby nodule in a rock matrix
	References
Index