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The GMRT
Subsections
An Overview of the GMRT
Introduction
Array Configuration
Receiver System
Digital Backends
GMRT Antennas and Feeds
Introduction
Types of Antennas
Characterizing Reflector Antennas
Computing Reflector Antenna Radiation Patterns
Aperture Efficiency
Design Specifications for the GMRT Antennas
Secondary Patterns
GMRT Feeds
Feed Placement
150 MHz Feed
327 MHz Feed
Dual-Frequency Coaxial Waveguide Feed
1000-1450 MHz Feed
GMRT Antenna Efficiencies
Further Reading
The GMRT Servo System
Introduction
Objectives of the GMRT Servo System
The GMRT Servo System Specifications
Control System Description
Closed Loop Control Systems
Principles of Position Control
Position Loop Amplifier
Rate Loop Amplifier
Current Loop Amplifier
Servo Amplifiers
Servo Motors
Gear Reducers
Position Sensors
Dual Drive
Digital Controller
Servo Operational Commands
GMRT Receivers
Introduction
Overview of the GMRT Receiver Chain
Receiver Design Considerations
The Multi Frequency Front Ends
The Antenna Base Receiver
The Fiber-Optic Link
The GMRT Optical Fiber System
Introduction
The Laser Transmitter
Laser Specifications
The Optical Fiber
The Optical Receiver
Link Performance
Local Oscillator and Base-band Systems
Requirement for a Local Oscillator System at the GMRT
The Frequency Translation Scheme used at the GMRT
Generation of Phase-Coherent Local Oscillator Signals
Noise Calibration and Walsh Switching
The Base-band System
A Summary of Important Specifications
Array Frequency Reference
First LO Synthesiser
Second and Third LO Sources and Offset Frequency Sources
Fourth LO Synthesiser
Base-band System
A Control and Monitor System for the GMRT
Introduction
Overview
ONLINE
PCROUTER
COMH
ANTCOM or ABC
Servo Control Computer
Monitor and Control Modules
Signal Flow in the GMRT Control & Monitor System
Error Detection
Signal Modulation
Frequency Shift Keying
System specifications of the Control & Monitor system
Overview
Bit rates available for various services
Details of the various communication links
The GMRT Correlator
Introduction
An overview of the GMRT Correlator
ADC
Delay-DPC
FFT
MAC
Modes of operation of the GMRT correlator
Non-Polar Mode
Indian-Polar Mode
Polar Mode
Further Reading
The Data Acquisition System for the GMRT
Data Acquisition
Correlator Control
Monitoring the health of the correlator
Online processing of the data
The network of acquisition and processing
The software layout
The low level programs
The high level programs
The peripheral programs on the network
Sequence of program execution
Time stamping of data and it's accuracy
Further desirable features
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An Overview of the
Up:
LFRA
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Further Reading
Contents
NCRA-TIFR
