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Spectrometer PDR. – The preliminary Design. John Ford (NRAO). Why a New Spectrometer?. Summary of Required Observing Modes. Overall Block Diagram. Analog System. Adapts output of Converter Modules to the ADC Low-pass filter Amplification Test tone injection Clock distribution - PowerPoint PPT Presentation
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Atacama Large Millimeter/submillimeter Array
Expanded Very Large ArrayRobert C. Byrd Green Bank Telescope
Very Long Baseline Array
Spectrometer PDR
John Ford (NRAO)
– The preliminary Design
Why a New Spectrometer?New Spectrometer Old GBT Spectrometer
Polyphase Filter Bank for RFI rejection Autocorrelation Spectrometer
256 level samplers 3 level samplers
16 high-speed samplers 8 high-speed samplers
1350 MHz bandwidth/sampler 800 MHz bandwidth/sampler
800 MB/s max disk I/O rate < 25 MB/s max disk I/O rate
New technology (FPGA based, Virtex-{5,6} Designed and built in early 1990’s
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Summary of Required Observing Modes
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Overall Block Diagram
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Analog System
• Adapts output of Converter Modules to the ADC– Low-pass filter– Amplification– Test tone injection
• Clock distribution– Split and amplify clock signal– Distribute to all ROACH boards
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Roach Assembly
ROACH Block Diagram
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ROACH 2
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3 GS/s ADC Board
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Clock Synthesizer Board
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Fujitsu Switch in its Natural Environment
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Computing Nodes
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Nehalem Node
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Storage Subsystem
• Project will supply ~100 TB of disk subsystems– Connected to 10 GbEthernet– Fast enough to support writing directly into subsystem
for most observing (But not pulsar searching)– Data accessible for astronomers simultaneously with
spectrometer use
• Project will not supply– VAO integration– Archiving software or methodology– Long-term storage media
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Preliminary Design Work
• Developing support hardware– IF system interface
• Anti-alias low-pass filters• Noise/test signal injection• Amplification
– Analog to Digital Converter sampling clock generation/distribution
– 1 Pulse Per Second distribution– Packaging
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Preliminary Design Work• Concentrating on the hard parts
– 3 GS/s sampling and PFB/FFT calculations– Heterogeneous Computing Approach
• Divide processing into front/back ends• Use FPGAs to fully process bandwidths greater than
200 MHz• Use FPGA front-ends to pre-process, split and
packetize data, then GPUs to provide fine channelization on narrower chunks
– Software Design• Adapting concepts and code from the Green Bank
Ultimate Pulsar Processing Instrument (GUPPI)• Adding support for the K-band FPA processing
pipeline• Integrating with the GBT Monitor and Control System
for user ease.16
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