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VLBA 4-Gbps Upgrade

VLBA 4-Gbps Upgrade. Jon Romney NRAO, Socorro EVN DBBC CDR Bologna 2007 / 4 / 24. VLBA 4-Gbps Upgrade Overview. Replace All Equipment Downstream from IFs Wideband Sampler/Filter module. 2x 500-MHz inputs; 4-Gbps output. Replacing BBCs / Samplers / Formatter. Further details to follow.

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VLBA 4-Gbps Upgrade

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  1. VLBA 4-Gbps Upgrade Jon Romney NRAO, Socorro EVN DBBC CDR Bologna 2007 / 4 / 24

  2. VLBA 4-Gbps UpgradeOverview • Replace All Equipment Downstream from IFs • Wideband Sampler/Filter module. • 2x 500-MHz inputs; 4-Gbps output. • Replacing BBCs / Samplers / Formatter. • Further details to follow. • Wideband Recording system. • Disk-based; 4-Gbps capacity; “Mark 5C”. • Compatible with existing Mark 5 module pool. • Wideband Correlator. • Stand-alone mini-WIDAR – OR – software/cluster system. • Wider bandwidth / higher spectral resolution / more flexible. EVN DBBC CDR

  3. VLBA 4-Gbps UpgradeFunding & Schedule • Funding Status • Wideband Sampler/Filter module. • Design development funded. • Implementation funding requested*. • Wideband Recording system. • Design funding requested*. • Wideband Correlator. • Software correlator completion funded. • Implementation funding requested* for intermediate cluster. • * funds requested from GBT track warranty arbitration payment. • Target Completion Date • … for all 3 prototypes: 2007 / 12 / 31. EVN DBBC CDR

  4. Wideband Sampler/FilterBasic VLBA Requirements • IF Input • Minimal: 2 x 500 MHz. • Optional: 4 x 500 MHz for dual-band dual-polar (etc.) modes. • Sampling • Sample clock: 1024 MHz. • Sample precision: 8 bits. • Filtering: Two Selectable Modes • Polyphase filter bank, spanning contiguous 500-MHz band. • Tunable “digital BBC” filters: 8 (possibly 16). • Bandwidths 62.5 kHz – 256 MHz / tunable to 1% of bandwidth. • Output truncation: 1 – 8 bits/sample. EVN DBBC CDR

  5. Wideband Sampler/FilterConcept History • Original • Exploit experience developed at NRAO from EVLA project. • Adapt relevant portions of EVLA data transmission system & correlator designs. • Haystack Collaboration • Similarities to Haystack DBE recognized. • Joint development of “DBE-2” selected as excellent opportunity for collaboration. • … at first NRAO/Haystack Technical Meeting, 2006 / 10 / 25 – 26. EVN DBBC CDR

  6. Wideband Sampler/FilterVLBA Concept History [2] • Modification for VLBI-2010 Requirements • Doubled input bandwidths to total 4 x 1 GHz. • Doubled sampler clock to 2048 MHz. • Added 10G Ethernet output, channel-packetized. • Required largest Xilinx Virtex 5 chip & corner-turner memories. • Required 2-board configuration for full capability. EVN DBBC CDR

  7. Most Recent NRAO-Haystack“DBE-2” Block Diagram EVN DBBC CDR

  8. Wideband Sampler/FilterVLBA Concept History [3] • Impact of iBob-2 • Discovered Casper group’s iBob-2 development recently. • Recognized similarities to most recent NRAO-Haystack board. • Development timescale a concern at NRAO. • Had hoped to complete prototype board by 2007 / 9 / 30. • Resolution currently not clear. EVN DBBC CDR

  9. Compatibility & Collaboration Considerations • Compatibility among DBBC/DBE Devices • NOT nearly as critical as recording systems. • No media to be interchanged. • But identical filter profiles important for optimal baseline closure. • Possible global agreement on filter characteristics. • Would require all devices to support same minimum number of taps. • Collaboration on Common Elements • Possible sharing of FPGA code for filters. • Would require all devices to use compatible FPGAs. EVN DBBC CDR

  10. Thank you EVN DBBC CDR

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