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The ALMA Data Transmission System – Digital Portion

The ALMA Data Transmission System – Digital Portion. Chris Langley ALMA Back End Integrated Product Team. The Challenge. Transmit 4 – 12 GHz Astronomical Data from the Front End (FE) Band Cartridges to the Correlator using Commercial Off The Shelf equipment wherever possible. The Challenge.

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The ALMA Data Transmission System – Digital Portion

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  1. The ALMA Data Transmission System – Digital Portion Chris Langley ALMA Back End Integrated Product Team National Radio Science Meetings

  2. The Challenge Transmit 4 – 12 GHz Astronomical Data from the Front End (FE) Band Cartridges to the Correlator using Commercial Off The Shelf equipment wherever possible. National Radio Science Meetings

  3. The Challenge Transmit 4 – 12 GHz Astronomical Data from the Front End (FE) Band Cartridges to the Correlator using Commercial Off The Shelf equipment wherever possible. The Proposal Convert FE data Digitally and Optically prior to transmission from each of 66 antennas. National Radio Science Meetings

  4. The Flaw COTS, or any other, D/A converters capable of 4 – 12 GHz inputs were not available during R&D. National Radio Science Meetings

  5. The Flaw COTS, or any other, D/A converters capable of 4 – 12 GHz inputs were not available during R&D. The Solution Separate, or Down Convert, the 4 – 12 GHz two polarity band into eight 2 – 4 GHz basebands prior to data conversion and transmission. National Radio Science Meetings

  6. Astronomical Data Down Conversion & Transmission National Radio Science Meetings

  7. Data Transmission System National Radio Science Meetings

  8. Design Considerations (1/2) • Operate at OC-192 (9.95328Gb/s) optical fiber signaling speed National Radio Science Meetings

  9. Design Considerations (1/2) • Operate at OC-192 (9.95328Gb/s) optical fiber signaling speed • Use of time division digital multiplexing to transform the input signaling rate to the channel signaling rate National Radio Science Meetings

  10. Design Considerations (1/2) • Operate at OC-192 (9.95328Gb/s) optical fiber signaling speed • Use of time division digital multiplexing to transform the input signaling rate to the channel signaling rate • Insertion of fill bits to convert input rate to signaling rate National Radio Science Meetings

  11. Design Considerations (1/2) • Operate at OC-192 (9.95328Gb/s) optical fiber signaling speed • Use of time division digital multiplexing to transform the input signaling rate to the channel signaling rate • Insertion of fill bits to convert input rate to signaling rate • Use of time division digital de-multiplexing to transform the channel signaling rate to the output signaling rate National Radio Science Meetings

  12. Design Considerations (1/2) • Operate at OC-192 (9.95328Gb/s) optical fiber signaling speed • Use of time division digital multiplexing to transform the input signaling rate to the channel signaling rate • Insertion of fill bits to convert input rate to signaling rate • Use of time division digital de-multiplexing to transform the channel signaling rate to the output signaling rate • Elimination of un-needed fill bits upon reception National Radio Science Meetings

  13. Design Considerations (1/2) • Operate at OC-192 (9.95328Gb/s) optical fiber signaling speed • Use of time division digital multiplexing to transform the input signaling rate to the channel signaling rate • Insertion of fill bits to convert input rate to signaling rate • Use of time division digital de-multiplexing to transform the channel signaling rate to the output signaling rate • Elimination of un-needed fill bits upon reception • Use of three OC-192 channels per 2 GHz baseband to achieve required capacity National Radio Science Meetings

  14. Design Considerations (2/2) • Low-voltage differential signaling (LVDS) • Fast rise/fall times • Noise resistant National Radio Science Meetings

  15. Design Considerations (2/2) • Low-voltage differential signaling (LVDS) • Fast rise/fall times • Noise resistant • Multiple FPGA design per channel • More economical than single FPGA • Ball Grid Array package  Lots of IO • 625+ MHz input signal capability National Radio Science Meetings

  16. Design Considerations (2/2) • Low-voltage differential signaling (LVDS) • Fast rise/fall times • Noise resistant • Multiple FPGA design per channel • More economical than single FPGA • Ball Grid Array package • 625+ MHz input signal capability • Commercial Optical “Half” Transponders • Change from original design • Became economical • Built in mux /demux, clock recovery National Radio Science Meetings

  17. Design Considerations (2/2) • Low-voltage differential signaling (LVDS) • Fast rise/fall times • Noise resistant • Multiple FPGA design per channel • More economical than single FPGA • Ball Grid Array package • 625+ MHz input signal capability • Commercial Optical “Half” Transponders • Economical • Built in mux /demux, clock recovery • Air cooled (flow through) module, RFI shielded (-50 dBm) National Radio Science Meetings

  18. Data Frame Organization National Radio Science Meetings

  19. Data Transmission SystemCloser View National Radio Science Meetings

  20. Data Transmitter Module(Digitizer and Formatter, 4 per Antenna) National Radio Science Meetings

  21. Data Transmitter Module4 / Antenna National Radio Science Meetings

  22. Digitizer AssemblyUniversity of Bordeaux National Radio Science Meetings

  23. Formatter with 3 Optical Transmitting Transponders National Radio Science Meetings

  24. Data Receiver Module(De-Formatter with 3 Optical Receiving Transponders) National Radio Science Meetings

  25. Data Receiver Module4 / Antenna National Radio Science Meetings

  26. DTS Modules for 1 Antenna Digitizer Clock IRAM, NRAO Fiber Optic Amplifier / Demultiplexer Jodrell Bank Observatory Fiber Optic Multiplexer Jodrell Bank Observatory Data Transmitters U of Bordeaux, NRAO Data Receivers NRAO National Radio Science Meetings

  27. DTS Link Tests - ALMA Antenna to LabChile, 8/2008 National Radio Science Meetings

  28. DTS Link Tests - ALMA Antenna to LabChile, 8/2008 National Radio Science Meetings

  29. Things We’d Do Differently … • Single FPGA per channel! • FPGA logic timing is difficult • Economics will likely catch up • Closer interaction between hardware and firmware designers • Each should be the other’s backup • Invite external expert’s opinions sooner during the design process • Test Stand • Design and build once assembly form factors are determined • Communication between remote team members was good, but could have been better • Specify an early DTS design review for the international partners National Radio Science Meetings

  30. Acknowledgements • Robert Freund, Principle Engineer, Arizona Radio Observatory • Paula Metzner, DTS Product Engineer, Atacama Large Millimeter Array, National Radio Astronomy Observatory … and the entire DTS teams from North America, the University of Bordeaux, IRAM (Grenoble, FR), and Jodrell Bank Observatory (~Manchester, UK). References R. W. Freund, ALMA Memo 420: Digital Transmission System Signaling Protocol, 2002 R. W. Freund and C. Langley, BE Critical Design Review, 2004. National Radio Science Meetings

  31. Auxiliary Slides National Radio Science Meetings

  32. Data Transmission System Overview The Partners National Radio Science Meetings

  33. System Requirements • Repeatable latency with no loss of samples National Radio Science Meetings

  34. System Requirements • Repeatable latency with no loss of samples • Bit error rate < 10-6 (End of Life) National Radio Science Meetings

  35. System Requirements • Repeatable latency with no loss of samples • Bit error rate < 10-6 (End of Life) • Multi-channel synchronization loss < 10-4 s National Radio Science Meetings

  36. System Requirements • Repeatable latency with no loss of samples • Bit error rate < 10-6 (End of Life) • Multi-channel synchronization loss < 10-4 s • 16 GHz analog bandwidth source National Radio Science Meetings

  37. System Requirements • Repeatable latency with no loss of samples • Bit error rate < 10-6 (End of Life) • Multi-channel synchronization loss < 10-4 s • 16 GHz analog bandwidth source • Nyquist sampled data National Radio Science Meetings

  38. System Requirements • Repeatable latency with no loss of samples • Bit error rate < 10-6 (End of Life) • Multi-channel synchronization loss < 10-4 s • 16 GHz analog bandwidth source • Nyquist sampled data • 3-bit data word National Radio Science Meetings

  39. System Requirements • Repeatable latency with no loss of samples • Bit error rate < 10-6 (End of Life) • Multi-channel synchronization loss < 10-4 s • 16 GHz analog bandwidth source • Nyquist sampled data • 3-bit data word • Data transmission synchronized with ALMA timing National Radio Science Meetings

  40. System OverviewExplicit requirements • 4 GSa/s per 2 GHz bandwidth IF channel National Radio Science Meetings

  41. System OverviewExplicit requirements • 4 GSa/s per 2 GHz bandwidth IF channel • 3 bits per sample National Radio Science Meetings

  42. System OverviewExplicit requirements • 4 GSa/s per 2 GHz bandwidth IF channel • 3 bits per sample • 2 Polarizations x 4 IF channels National Radio Science Meetings

  43. System OverviewExplicit requirements • 4 GSa/s per 2 GHz bandwidth IF channel • 3 bits per sample • 2 Polarizations x 4 IF channels • 96 Gb/s per antenna (120 Gb/s encoded data) National Radio Science Meetings

  44. System OverviewExplicit requirements • 4 GSa/s per 2 GHz bandwidth IF channel • 3 bits per sample • 2 Polarizations x 4 IF channels • 96 Gb/s per antenna (120 Gb/s encoded data) • 250 MHz input word rate (96-bit wide parallel word) National Radio Science Meetings

  45. System OverviewExplicit requirements • 4 GSa/s per 2 GHz bandwidth IF channel • 3 bits per sample • 2 Polarizations x 4 IF channels • 96 Gb/s per antenna (120 Gb/s encoded data) • 250 MHz input word rate (96-bit wide parallel word) • 125 MHz output word rate (192-bit wide parallel word) National Radio Science Meetings

  46. System OverviewExplicit requirements • 4 GSa/s per 2 GHz bandwidth IF channel • 3 bits per sample • 2 Polarizations x 4 IF channels • 96 Gb/s per antenna (120 Gb/s encoded data) • 250 MHz input word rate (96-bit wide parallel word) • 125 MHz output word rate (192-bit wide parallel word) • Grouping of a polarization pair: 24 Gb/s per pair National Radio Science Meetings

  47. System OverviewExplicit requirements • 4 GSa/s per 2 GHz bandwidth IF channel • 3 bits per sample • 2 Polarizations x 4 IF channels • 96 Gb/s per antenna (120 Gb/s encoded data) • 250 MHz input word rate (96-bit wide parallel word) • 125 MHz output word rate (192-bit wide parallel word) • Grouping of a polarization pair: 24 Gb/s per pair • Walsh function 180° switching National Radio Science Meetings

  48. System OverviewExplicit requirements • 4 GSa/s per 2 GHz bandwidth IF channel • 3 bits per sample • 2 Polarizations x 4 IF channels • 96 Gb/s per antenna (120 Gb/s encoded data) • 250 MHz input word rate (96-bit wide parallel word) • 125 MHz output word rate (192-bit wide parallel word) • Grouping of a polarization pair: 24 Gb/s per pair • Walsh function 180° switching • 15 Km (maximum) distance National Radio Science Meetings

  49. System OverviewImplied requirements • Configurable if not deterministic timing (repeatable latency) National Radio Science Meetings

  50. System OverviewImplied requirements • Configurable if not deterministic timing (repeatable latency) • Fast frame synchronization National Radio Science Meetings

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