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 Correlator Switch-ON
 Correlator Switch-OFF
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 Modular Board (PKTz)
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 eGMRT
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Current Status

 Status - 20 Feb. 2018
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Publications

 IETE - Real Time Broadband RFI excision for GWB
 JAI - Real Time Impulsive RFI Mitigation for Radio Telescopes
 IEEE - Real Time RFI Excision for GWB
 JAI - Wideband Digital Backend for GMRT
 EA - Real-time Software Backend for the GMRT

GMRT INTRODUCTION

      NCRA has set up a unique facility for radio astronomical research using the metre wavelengths range of the radio spectrum, known as the Giant Metrewave Radio Telescope (GMRT). It is located at a site about 80 km north of Pune. GMRT consists of 30 fully steerable gigantic parabolic dishes of 45m diameter each spread over distances of upto 25 km. GMRT is one of the most challenging experimental programmes in basic sciences undertaken by Indian scientists and engineers.
  Apart from the novel low-cost design of the parabolic dishes, the instrument has state-of-the-art electronics systems developed indigenously and consisting of the following main sub units.
  1. Antenna feeds at six different frequency bands between 50 MHz and 1500 MHz, having good polarization characteristics as well as simultaneous multiband operation.
  2.Low-noise amplifiers, local oscillator synthesizers, mixers, IF amplifiers.
  3.Optical fibres linking the entire array with the CEB. These are used both for the telemetry signals and local oscillator phase reference communication between the CEB and each antenna base.
  4.Digital Backend (Correlator System).

Digital Backend:
    The initial design and development of correlator system started in the year of 1991. It was 2 antenne, then 4, 8, 16 and 32 antennae correlator. The 30-station single side-band, dual polarization, ~230,000 channel FX correlator has been installed in the CEB in August 1998. This correlator is designed to generate 128 spectral channels spread over a maximum bandwidth of 16 MHz for each of the polarizations. Fringe stopping and fractional sample time correction is done in the hardware. The design of the correlator for the second side-band started. Full pledged correlator of 30 antennae, both polarizations & 32MHz bandwidth started working since June 2002. This hardware correlator was mainly ASIC based FFT and MAC boards. A digital 2,30,000-channel FX-type correlator providing upto 128 spectral channels and covering a maximum bandwidth of 32 MHz. This backend also had the pulsar backend of Incorreherant array (IA) and Phased Array (PA).
  In the year 2009, GMRT Software Backend (GSB) integrated and released for internal observations, which was under design and development since 2003. Once this GSB system got stabilized, in the year 2010 the ASIC based correlator and pulsar systems dismantled forever. GSB system is the main backend being used for observations as on today.
  In the year 2006, started design and development of FPGA (ROACH boards) based correlator. Initially single board 2 antennae pocket correlator, then 4, 8 & 16 antennae packetized (multi modular) correlator built. The signle board design modified to use for 15 meter project at NCRA campus in the year 2014.   Apart from the design and development of these backends needed to upgrade the GMRT project capabilities, the group also done the study and development of many other projects like RFI mitigation algorith, temperature study and monitoring etc..

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