GMRT Back-end Systems - CASPER
GMRT Back-end Systems - CASPER
GMRT Back-end Systems - CASPER
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Digital <strong>Back</strong><strong>end</strong>s for <strong>GMRT</strong> UpgradeB. AjithkumarNCRA, Pune, India<strong>CASPER</strong> – 2009 Workshop, CapeTownSep 28, 2009
<strong>GMRT</strong> LocationThe Giant Metre-wave RadioTelescope (<strong>GMRT</strong>) is a worldclass instrument for studyingastrophysical phenomena atlow radio frequencies (50 to1450 MHz)• Longitude : 74 deg E• Latitude : 19 deg N• About 70 km N of Pune,160 km E of Mumbai.Sep 28, 2009Digital <strong>Back</strong><strong>end</strong>s for <strong>GMRT</strong> Upgrade 2
<strong>GMRT</strong> Array30 dishes; 45 m diameter• 12 dishes in centralcompact array• 18 dishes in 3 arms ofY-array1 km x 1km14km• Total extent : 14 kmradius ⇒ resolutioneq to 28 km size antenna.Sep 28, 2009Digital <strong>Back</strong><strong>end</strong>s for <strong>GMRT</strong> Upgrade 3
<strong>GMRT</strong> System Specifications 40 – 60 MHz 300 – 360 MHz120 – 180 MHz 580 – 650 MHz225 – 245 MHz 1000 – 1430 MHzSimultaneous observations in two polarisations each at abandwidth of 32 MHz.The observation band can be set with a resolution of 100 HzAntennas can be used in sub array mode of operation.Can track any source above 18deg elevation.Sep 28, 2009Digital <strong>Back</strong><strong>end</strong>s for <strong>GMRT</strong> Upgrade 4
Existing Digital Receiver at <strong>GMRT</strong>• Both <strong>Back</strong>-<strong>end</strong>s (FXCorrelator & PulsarReceiver) can operatesimultaneously.• Common signalprocessing stages: ADC,Delay correction, Fringestopping and FFT.Sep 28, 2009Digital <strong>Back</strong><strong>end</strong>s for <strong>GMRT</strong> Upgrade 5
System Parameters for the <strong>GMRT</strong>(in Synthesis Mode)150Frequency (MHz)2353276101420Primary Beam (deg)3.22.01.40.80.4Synthesized Beam (arcSec)2013952Effective Area (m 2 )30,00018,000System Temp ( o K)45018011010070RMS noise* in Image(µJy = 10 -32 W.m -2 .Hz -1-1 )4016111013Sep 28, 2009Digital <strong>Back</strong><strong>end</strong>s for <strong>GMRT</strong> Upgrade 6
<strong>GMRT</strong> : Usage Statistics• Total of 840 proposals from cycle 1 to 14 (about 12% of these rejected)• 24148.5 hrs of telescope time allotted for observations (out of a total of 58329.5hrs requested) -- factor of 2 oversubscription• Indian vs Foreign users : 60% vs 40% in the beginning ;now more like 40% vs 60% !Sep 28, 2009Digital <strong>Back</strong><strong>end</strong>s for <strong>GMRT</strong> Upgrade 7
<strong>GMRT</strong> Receiver UpgradeMajor upgrade to <strong>GMRT</strong> Receiver is planned so asto provide increased observational bandwidth,seamless frequency coverage, increased dynamicrange, reduce the electronics at remote sites.RF Electronics with Low Noise Front<strong>end</strong>s will belocated at the prime focus. The signals at RFfrequencies will be directly transported to centralstation using Broadband Analog Optical Fibercables. Further analog and digital processing willbe done at central station.Sep 28, 2009Digital <strong>Back</strong><strong>end</strong>s for <strong>GMRT</strong> Upgrade 8
<strong>GMRT</strong> Receiver UpgradeSep 28, 2009Digital <strong>Back</strong><strong>end</strong>s for <strong>GMRT</strong> Upgrade 9
Features : Comparison with Current SystemCurrent system Observation at specificfrequencies in 50 to 1500 Mhz Instantaneous Bandwidth of32 MHz in each polarisation. Facility for dual frequencyobservations with 32 Mhz ineach band. Receiverelectronicsdistributed between centralstation and remote antennasite.Upgraded System Seamless Coverage from 50to 1500 MHz. SupportsinstantaneousBandwidth of 400 MHz ineach polarisation. Facility for observations over400 MHz band widthscontinuous. Reduced electronics atremote sites.Sep 28, 2009Digital <strong>Back</strong><strong>end</strong>s for <strong>GMRT</strong> Upgrade 10
Simplified BlockSchematicSignal Processing atCentral Station Analog Processing Digitisation Digital Processing RFI Excision Signal MonitoringSep 28, 2009Digital <strong>Back</strong><strong>end</strong>s for <strong>GMRT</strong> Upgrade 11
<strong>GMRT</strong> Upgrade : Digital <strong>Back</strong><strong>end</strong>Requirements• Specifications :– 30 stations– 400 MHz BW (instantaneous)– 16 K Freq Channels– Full polar mode– Coarse and Fine Delay correction– Fringe rotation– Interferometer with dump times ~ 100 ms– Incoherent and Phased array beam outputs : at least 2 beamsfor each; with full time resolution– Pulsar back-<strong>end</strong>s attached to the beam outputsSep 28, 2009Digital <strong>Back</strong><strong>end</strong>s for <strong>GMRT</strong> Upgrade 12
<strong>GMRT</strong> Upgrade : Digital <strong>Back</strong><strong>end</strong>• Possibilities :– High speed ADCs + FPGA based back-<strong>end</strong>s– Hybrid system using FPGAs + CPU-based processing• Current status :– MOU with South Africa SKA on joint development,implementation and testing of a Eight antenna packetisedcorrelator prototype.– Team has built wide band correlators on FPGA boards andtested them using antenna signals.– Developed design blocks for use in correlatorimplementation.Sep 28, 2009Digital <strong>Back</strong><strong>end</strong>s for <strong>GMRT</strong> Upgrade 13
New Designs Implemented & TestedNew library blocks developed and added to<strong>CASPER</strong> library(1) Coarse Delay(2) Fine Delay + Fringe StopThese designs are incorporated in the pocketcorrelator design and tested in the lab as well as<strong>GMRT</strong> antenna signals.Sep 28, 2009Digital <strong>Back</strong><strong>end</strong>s for <strong>GMRT</strong> Upgrade 14
Test Setup for ADC +FPGA BoardsLabSep 28, 2009Digital <strong>Back</strong><strong>end</strong>s for <strong>GMRT</strong> Upgrade 15
2 Ant, 150 MHz with Int + Fract. DelayFFT Ch : 1KDelay : 6.8 uSFreq : 75-225 MHzSep 28, 2009Digital <strong>Back</strong><strong>end</strong>s for <strong>GMRT</strong> Upgrade 16
Test Results on iBOBSource : 3C48RF Band : 1060 MHzCombined IF signals used asinputs to ADCs.A – C08B – C09Sep 28, 2009Digital <strong>Back</strong><strong>end</strong>s for <strong>GMRT</strong> Upgrade 17
2 Ant, 300 MHz with Int + Fract. DelayFFT Ch : 512Delay : 13.6 uSFreq : 0-300 MHzSep 28, 2009Digital <strong>Back</strong><strong>end</strong>s for <strong>GMRT</strong> Upgrade 18
Noise Source Tests -iBOBSource : Broadband NoiseA – NoiseB – NoiseSelf and Cross plots withdifferent Delay settingsSep 28, 2009Digital <strong>Back</strong><strong>end</strong>s for <strong>GMRT</strong> Upgrade 19
Antenna Tests - iBOBSource : Cygnus A – C11 B – C04Self and Cross plots with different Delay settingsSep 28, 2009Digital <strong>Back</strong><strong>end</strong>s for <strong>GMRT</strong> Upgrade 20
Fringe Stop - iBOBSource : CygnusA – C11 B – C04Fringe StopSep 28, 2009Digital <strong>Back</strong><strong>end</strong>s for <strong>GMRT</strong> Upgrade 21
First fringes with aROACH !Source : CygnusA – C11 B – C04Self & CrossSep 28, 2009Digital <strong>Back</strong><strong>end</strong>s for <strong>GMRT</strong> Upgrade 22
CollaborationIn Dec 2008, members of Digital <strong>Back</strong><strong>end</strong> groupof South African SKA Project visited <strong>GMRT</strong> and wehad detailed discussions on possible collaborationbetween the two groups.Based on the discussions a MOU has been signedby both parties on developing an 8 antenna 400MHz <strong>Back</strong><strong>end</strong> during 2009-10 using <strong>CASPER</strong>tools.This will be useful as a digital back<strong>end</strong> at KATproject and will be tested at <strong>GMRT</strong> as finalprototype for the planned <strong>GMRT</strong> upgrades.Sep 28, 2009Digital <strong>Back</strong><strong>end</strong>s for <strong>GMRT</strong> Upgrade 23
Visit by SouthAfrican TeamSep 28, 2009Digital <strong>Back</strong><strong>end</strong>s for <strong>GMRT</strong> Upgrade 24
Proposed Functional SchematicSchematic DrawingCourtesy : JasonSep 28, 2009Digital <strong>Back</strong><strong>end</strong>s for <strong>GMRT</strong> Upgrade 25
Proposed<strong>Back</strong><strong>end</strong>High-speedstorage serversfor streamingraw data todisk for off-lineprocessing.The cluster ofservers canalso performthe function ofSoftware<strong>Back</strong><strong>end</strong>.Sep 28, 2009Schematic DrawingCourtesy : JasonDigital <strong>Back</strong><strong>end</strong>s for <strong>GMRT</strong> Upgrade 26
Thank You !!
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