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THÔNG TIN TÀI LIỆU
Cấu trúc
Preface to the Third Edition
Preface to the Second Edition
Preface to the First Edition
Contents
Abbreviations and Acronyms
Principal Symbols
1 Introduction and Historical Review
1.1 Applications of Radio Interferometry
1.2 Basic Terms and Definitions
1.2.1 Cosmic Signals
1.2.2 Source Positions and Nomenclature
1.2.3 Reception of Cosmic Signals
1.3 Development of Radio Interferometry
1.3.1 Evolution of Synthesis Techniques
1.3.2 Michelson Interferometer
1.3.3 Early Two-Element Radio Interferometers
1.3.4 Sea Interferometer
1.3.5 Phase-Switching Interferometer
1.3.6 Optical Identifications and Calibration Sources
1.3.7 Early Measurements of Angular Width
1.3.8 Early Survey Interferometers and the Mills Cross
1.3.9 Centimeter-Wavelength Solar Imaging
1.3.10 Measurements of Intensity Profiles
1.3.11 Spectral Line Interferometry
1.3.12 Earth-Rotation Synthesis Imaging
1.3.13 Development of Synthesis Arrays
1.3.14 Very-Long-Baseline Interferometry
1.3.15 VLBI Using Orbiting Antennas
1.4 Quantum Effect
Appendix 1.1 Sensitivity of Radio Astronomical Receivers (the Radiometer Equation)
Further Reading
Textbooks on Radio Astronomy and Radio Interferometry
Historical Reviews
General Interest
References
2 Introductory Theory of Interferometry and Synthesis Imaging
2.1 Planar Analysis
2.2 Effect of Bandwidth
2.3 One-Dimensional Source Synthesis
2.3.1 Interferometer Response as a Convolution
2.3.2 Convolution Theorem and Spatial Frequency
2.3.3 Example of One-Dimensional Synthesis
2.4 Two-Dimensional Synthesis
2.4.1 Projection-Slice Theorem
2.4.2 Three-Dimensional Imaging
Appendix 2.1 A Practical Fourier Transform Primer
A2.1.1 Useful Fourier Transform Pairs
A2.1.2 Basic Fourier Transform Properties
A2.1.3 Two-Dimensional Fourier Transform
A2.1.4 Fourier Series
A2.1.5 Truncated Functions
3 Analysis of the Interferometer Response
3.1 Fourier Transform Relationship Between Intensityand Visibility
3.1.1 General Case
3.1.2 East–West Linear Arrays
3.2 Cross-Correlation and the Wiener–Khinchin Relation
3.3 Basic Response of the Receiving System
3.3.1 Antennas
3.3.2 Filters
3.3.3 Correlator
3.3.4 Response to the Incident Radiation
Appendix 3.1 Mathematical Representation of Noiselike Signals
A3.1.1 Analytic Signal
A3.1.2 Truncated Function
4 Geometrical Relationships, Polarimetry, and the Interferometer Measurement Equation
4.1 Antenna Spacing Coordinates and (u,v) Loci
4.2 (u',v') Plane
4.3 Fringe Frequency
4.4 Visibility Frequencies
4.5 Calibration of the Baseline
4.6 Antennas
4.6.1 Antenna Mounts
4.6.2 Beamwidth and Beam-Shape Effects
4.7 Polarimetry
4.7.1 Antenna Polarization Ellipse
4.7.2 Stokes Visibilities
4.7.3 Instrumental Polarization
4.7.4 Matrix Formulation
4.7.5 Calibration of Instrumental Polarization
4.8 The Interferometer Measurement Equation
4.8.1 Multibaseline Formulation
Appendix 4.1 Hour Angle–Declination and Elevation–Azimuth Relationships
Appendix 4.2 Leakage Parameters in Terms of the Polarization Ellipse
A4.2.1 Linear Polarization
A4.2.2 Circular Polarization
5 Antennas and Arrays
5.1 Antennas
5.2 Sampling the Visibility Function
5.2.1 Sampling Theorem
5.2.2 Discrete Two-Dimensional Fourier Transform
5.3 Introductory Discussion of Arrays
5.3.1 Phased Arrays and Correlator Arrays
5.3.2 Spatial Sensitivity and the Spatial TransferFunction
5.3.3 Meter-Wavelength Cross and T-Shaped Arrays
5.4 Spatial Transfer Function of a Tracking Array
5.4.1 Desirable Characteristics of the Spatial Transfer Function
5.4.2 Holes in the Spatial Frequency Coverage
5.5 Linear Tracking Arrays
5.6 Two-Dimensional Tracking Arrays
5.6.1 Open-Ended Configurations
5.6.2 Closed Configurations
5.6.3 VLBI Configurations
5.6.4 Orbiting VLBI Antennas
5.6.5 Planar Arrays
5.6.6 Some Conclusions on Antenna Configurations
5.7 Implementation of Large Arrays
5.7.1 Low-Frequency Range
5.7.2 Midfrequency and Higher Ranges
5.7.2.1 Phased-Array Feeds
5.7.2.2 Optimum Antenna Size
5.7.3 Development of Extremely Large Arrays
5.7.4 The Direct Fourier Transform Telescope
6 Response of the Receiving System
6.1 Frequency Conversion, Fringe Rotation,and Complex Correlators
6.1.1 Frequency Conversion
6.1.2 Response of a Single-Sideband System
6.1.3 Upper-Sideband Reception
6.1.4 Lower-Sideband Reception
6.1.5 Multiple Frequency Conversions
6.1.6 Delay Tracking and Fringe Rotation
6.1.7 Simple and Complex Correlators
6.1.8 Response of a Double-Sideband System
6.1.9 Double-Sideband System with Multiple Frequency Conversions
6.1.10 Fringe Stopping in a Double-Sideband System
6.1.11 Relative Advantages of Double- and Single-Sideband Systems
6.1.12 Sideband Separation
6.2 Response to the Noise
6.2.1 Signal and Noise Processing in the Correlator
6.2.2 Noise in the Measurement of Complex Visibility
6.2.3 Signal-to-Noise Ratio in a Synthesized Image
6.2.4 Noise in Visibility Amplitude and Phase
6.2.5 Relative Sensitivities of Different Interferometer Systems
6.2.6 System Temperature Parameter α
6.3 Effect of Bandwidth
6.3.1 Imaging in the Continuum Mode
6.3.2 Wide-Field Imaging with a Multichannel System
6.4 Effect of Visibility Averaging
6.4.1 Visibility Averaging Time
6.4.2 Effect of Time Averaging
6.5 Speed of Surveying
Appendix 6.1 Partial Rejection of a Sideband
7 System Design
7.1 Principal Subsystems of the Receiving Electronics
7.1.1 Low-Noise Input Stages
7.1.2 Noise Temperature Measurement
7.1.3 Local Oscillator
7.1.4 IF and Signal Transmission Subsystems
7.1.5 Optical Fiber Transmission
7.1.6 Delay and Correlator Subsystems
7.2 Local Oscillator and General Considerationsof Phase Stability
7.2.1 Round-Trip Phase Measurement Schemes
7.2.2 Swarup and Yang System
7.2.3 Frequency-Offset Round-Trip System
7.2.4 Automatic Correction System
7.2.5 Fiberoptic Transmission of LO Signals
7.2.6 Phase-Locked Loops and Reference Frequencies
7.2.7 Phase Stability of Filters
7.2.8 Effect of Phase Errors
7.3 Frequency Responses of the Signal Channels
7.3.1 Optimum Response
7.3.2 Tolerances on Variation of the Frequency Response: Degradation of Sensitivity
7.3.3 Tolerances on Variation of the Frequency Response: Gain Errors
7.3.4 Delay and Phase Errors in Single- and Double-Sideband Systems
7.3.5 Delay Errors and Tolerances
7.3.6 Phase Errors and Degradation of Sensitivity
7.3.7 Other Methods of Mitigation of Delay Errors
7.3.8 Multichannel (Spectral Line) Correlator Systems
7.3.9 Double-Sideband Systems
7.4 Polarization Mismatch Errors
7.5 Phase Switching
7.5.1 Reduction of Response to Spurious Signals
7.5.2 Implementation of Phase Switching
7.5.3 Timing Accuracy in Phase Switching
7.5.4 Interaction of Phase Switching with Fringe Rotation and Delay Adjustment
7.6 Automatic Level Control and Gain Calibration
7.7 Fringe Rotation
Appendix 7.1 Sideband-Separating Mixers
Appendix 7.2 Dispersion in Optical Fiber
Appendix 7.3 Alias Sampling
8 Digital Signal Processing
8.1 Bivariate Gaussian Probability Distribution
8.2 Periodic Sampling
8.2.1 Nyquist Rate
8.2.2 Correlation of Sampled but UnquantizedWaveforms
8.3 Sampling with Quantization
8.3.1 Two-Level Quantization
8.3.2 Four-Level Quantization
8.3.3 Three-Level Quantization
8.3.4 Quantization Efficiency: Simplified Analysis for Four or More Levels
8.3.5 Quantization Efficiency: Full Analysis, Three or More Levels
8.3.6 Correlation Estimates for Strong Sources
8.4 Further Effects of Quantization
8.4.1 Correlation Coefficient for Quantized Data
8.4.2 Oversampling
8.4.3 Quantization Levels and Data Processing
8.5 Accuracy in Digital Sampling
8.5.1 Tolerances in Digital Sampling Levels
8.6 Digital Delay Circuits
8.7 Quadrature Phase Shift of a Digital Signal
8.8 Digital Correlators
8.8.1 Correlators for Continuum Observations
8.8.2 Digital Spectral Line Measurements
8.8.3 Lag (XF) Correlator
8.8.4 FX Correlator
8.8.5 Comparison of XF and FX Correlators
8.8.6 Hybrid Correlator
8.8.7 Demultiplexing in Broadband Correlators
8.8.8 Examples of Bandwidths and Bit DataQuantization
8.8.9 Polyphase Filter Banks
8.8.10 Software Correlators
Appendix 8.1 Evaluation of ∞q=1R2∞(qτs)
Appendix 8.2 Probability Integral for Two-Level Quantization
Appendix 8.3 Optimal Performance for Four-Level Quantization
Appendix 8.4 Introduction to the Discrete Fourier Transform
A8.4.1 Response to a Complex Sine Wave
A8.4.2 Padding with Zeros
9 Very-Long-Baseline Interferometry
9.1 Early Development
9.2 Differences Between VLBI and Conventional Interferometry
9.2.1 The Problem of Field of View
9.3 Basic Performance of a VLBI System
9.3.1 Time and Frequency Errors
9.3.2 Retarded Baselines
9.3.3 Noise in VLBI Observations
9.3.4 Probability of Error in the Signal Search
9.3.5 Coherent and Incoherent Averaging
9.4 Fringe Fitting for a Multielement Array
9.4.1 Global Fringe Fitting
9.4.2 Relative Performance of Fringe DetectionMethods
9.4.3 Triple Product, or Bispectrum
9.4.4 Fringe Searching with a Multielement Array
9.4.5 Multielement Array with Incoherent Averaging
9.5 Phase Stability and Atomic Frequency Standards
9.5.1 Analysis of Phase Fluctuations
9.5.2 Oscillator Coherence Time
9.5.3 Precise Frequency Standards
9.5.4 Rubidium and Cesium Standards
9.5.5 Hydrogen Maser Frequency Standard
9.5.6 Local Oscillator Stability
9.5.7 Phase Calibration System
9.5.8 Time Synchronization
9.6 Data Storage Systems
9.7 Processing Systems and Algorithms
9.7.1 Fringe Rotation Loss (ηR)
9.7.2 Fringe Sideband Rejection Loss (ηS)
9.7.3 Discrete Delay Step Loss (ηD)
9.7.4 Summary of Processing Losses
9.8 Bandwidth Synthesis
9.8.1 Burst Mode Observing
9.9 Phased Arrays as VLBI Elements
9.10 Orbiting VLBI (OVLBI)
9.11 Satellite Positioning
10 Calibration and Imaging
10.1 Calibration of the Visibility
10.1.1 Corrections for Calculable or Directly Monitored Effects
10.1.2 Use of Calibration Sources
10.2 Derivation of Intensity from Visibility
10.2.1 Imaging by Direct Fourier Transformation
10.2.2 Weighting of the Visibility Data
10.2.2.1 Robust Weighting
10.2.3 Imaging by Discrete Fourier Transformation
10.2.4 Convolving Functions and Aliasing
10.2.5 Aliasing and the Signal-to-Noise Ratio
10.2.6 Wide-Field Imaging
10.3 Closure Relationships
10.4 Visibility Model Fitting
10.4.1 Basic Considerations for Simple Models
10.4.2 Examples of Parameter Fitting to Models
10.4.3 Modeling Azimuthally Symmetric Sources
10.4.4 Modeling of Very Extended Sources
10.5 Spectral Line Observations
10.5.1 VLBI Observations of Spectral Lines
10.5.2 Variation of Spatial Frequency Over theBandwidth
10.5.3 Accuracy of Spectral Line Measurements
10.5.4 Presentation and Analysis of Spectral LineObservations
10.6 Miscellaneous Considerations
10.6.1 Interpretation of Measured Intensity
10.6.2 Ghost Images
10.6.3 Errors in Images
10.6.4 Hints on Planning and Reduction of Observations
10.7 Observations of Cosmological Fine Structure
10.7.1 Cosmic Microwave Background
10.7.2 Epoch of Reionization
Appendix 10.1 The Edge of the Moon as a Calibration Source
Appendix 10.2 Doppler Shift of Spectral Lines
Appendix 10.3 Historical Notes
A10.3.1 Images from One-Dimensional Profiles
A10.3.2 Analog Fourier Transformation
11 Further Imaging Techniques
11.1 The CLEAN Deconvolution Algorithm
11.1.1 CLEAN Algorithm
11.1.2 Implementation and Performance of the CLEAN Algorithm
11.2 Maximum Entropy Method
11.2.1 MEM Algorithm
11.2.2 Comparison of CLEAN and MEM
11.2.3 Further Deconvolution Procedures
11.3 Adaptive Calibration and Imaging
11.3.1 Hybrid Imaging
11.3.2 Self-Calibration
11.3.3 Imaging with Visibility Amplitude Data Only
11.4 Imaging with High Dynamic Range
11.5 Mosaicking
11.5.1 Methods of Producing the Mosaic Image
11.5.2 Short-Baseline Measurements
11.6 Multifrequency Synthesis
11.7 Noncoplanar Baselines
11.8 Some Special Techniques of Image Analysis
11.8.1 Use of CLEAN and Self-Calibration with Spectral Line Data
11.8.2 A-Projection
11.8.3 Peeling
11.8.4 Low-Frequency Imaging
11.8.5 Lensclean
11.8.6 Compressed Sensing
12 Interferometer Techniques for Astrometry and Geodesy
12.1 Requirements for Astrometry
12.1.1 Reference Frames
12.2 Solution for Baseline and Source-Position Vectors
12.2.1 Phase Measurements
12.2.2 Measurements with VLBI Systems
12.2.3 Phase Referencing (Position)
12.2.4 Phase Referencing (Frequency)
12.3 Time and Motion of the Earth
12.3.1 Precession and Nutation
12.3.2 Polar Motion
12.3.3 Universal Time
12.3.4 Measurement of Polar Motion and UT1
12.4 Geodetic Measurements
12.5 Proper Motion and Parallax Measurements
12.6 Solar Gravitational Deflection
12.7 Imaging Astronomical Masers
Appendix 12.1 Least-Mean-Squares Analysis
A12.1.1 Linear Case
A12.1.2 Nonlinear Case
A12.1.3 (u,v) vs. Image Plane Fitting
Appendix 12.2 Second-Order Effects in Phase Referencing
13 Propagation Effects: Neutral Medium
13.1 Theory
13.1.1 Basic Physics
13.1.2 Refraction and Propagation Delay
13.1.3 Absorption
13.1.4 Origin of Refraction
13.1.5 Radio Refractivity
13.1.6 Phase Fluctuations
13.1.7 Kolmogorov Turbulence
13.1.8 Anomalous Refraction
13.2 Site Evaluation and Data Calibration
13.2.1 Opacity Measurements
13.2.2 Site Testing by Direct Measurementof Phase Stability
13.3 Calibration via Atmospheric Emission
13.3.1 Continuum Calibration
13.3.2 22-GHz Water-Vapor Radiometry
13.3.3 183-GHz Water-Vapor Radiometry
13.4 Reduction of Atmospheric Phase Errors by Calibration
Appendix 13.1 Importance of the 22-GHz Line in WWII Radar Development
Appendix 13.2 Derivation of the Tropospheric Phase Structure Function
14 Propagation Effects: Ionized Media
14.1 Ionosphere
14.1.1 Basic Physics
14.1.2 Refraction and Propagation Delay
14.1.3 Calibration of Ionospheric Delay
14.1.4 Absorption
14.1.5 Small- and Large-Scale Irregularities
14.2 Scattering Caused by Plasma Irregularities
14.2.1 Gaussian Screen Model
14.2.2 Power-Law Model
14.3 Interplanetary Medium
14.3.1 Refraction
14.3.2 Interplanetary Scintillation (IPS)
14.4 Interstellar Medium
14.4.1 Dispersion and Faraday Rotation
14.4.2 Diffractive Scattering
14.4.3 Refractive Scattering
Appendix 14.1 Refractive Bending in the Ionosphere
15 Van Cittert–Zernike Theorem, Spatial Coherence,and Scattering
15.1 Van Cittert–Zernike Theorem
15.1.1 Mutual Coherence of an Incoherent Source
15.1.2 Diffraction at an Aperture and the Response of an Antenna
15.1.3 Assumptions in the Derivation and Application of the van Cittert–Zernike Theorem
15.2 Spatial Coherence
15.2.1 Incident Field
15.2.2 Source Coherence
15.2.3 Completely Coherent Source
15.3 Scattering and the Propagation of Coherence
16 Radio Frequency Interference
16.1 Detection of Interference
16.1.1 Low-Frequency Radio Environment
16.2 Removal of Interference
16.2.1 Nulling for Attenuation of Interfering Signals
16.2.2 Further Considerations of Deterministic Nulling
16.2.3 Adaptive Nulling in the Synthesized Beam
16.3 Estimation of Harmful Thresholds
16.3.1 Short- and Intermediate-Baseline Arrays
16.3.2 Fringe-Frequency Averaging
16.3.3 Decorrelation of Broadband Signals
16.4 Very-Long-Baseline Systems
16.5 Interference from Airborne and Space Transmitters
16.6 Regulation of the Radio Spectrum
17 Related Techniques
17.1 Intensity Interferometer
17.2 Lunar Occultation Observations
17.3 Measurements on Antennas
17.4 Detection and Tracking of Space Debris
17.5 Earth Remote Sensing by Interferometry
17.6 Optical Interferometry
17.6.1 Instruments and Their Usage
17.6.2 Sensitivity of Direct Detection and Heterodyne Systems
17.6.3 Optical Intensity Interferometer
17.6.4 Speckle Imaging
Further Reading in Optical Interferometry
Author Index
Subject Index
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