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CABB, The Instrument

Explore the detailed evolution of the CSIRO CABB instrument, from its inception to current operations. Delve into the technological advancements, changes, and improvements in antenna control, correlator systems, and data processing.

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CABB, The Instrument

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  1. CABB, The Instrument Dick Ferris, Warwick Wilson and the CABB Team 13 May 2009

  2. A little recent history • CABB at large • A bit more detail • What to expect • Beginning May 23, 2008 ... CSIRO. CABB, The Instrument

  3. First Fringes 1, H20 in Orion, 22.235GHz CA02 Auto CA02 A pol X CA03 B pol ! CSIRO. CABB, The Instrument

  4. First Fringes 2, Both A pol Amplitude up x100 CSIRO. CABB, The Instrument

  5. First Fringes 3, 0727-115 (4Jy) CSIRO. CABB, The Instrument

  6. First Image 5 Antennas 128MHz 4 Stokes Good match to ATCORR image CSIRO. CABB, The Instrument

  7. Antennas What’s different: • New conversion system : Simple one step - for 6/3cm - or two step – for other bands • Fringe rotation and fine delay system removed • Only one bandwidth = 2GHz • 2-bit digitisers replaced by 9-bit ADCs • 2 Gb/s data to central site increased to 160Gb/s What’s remained: • Feeds and Frontends • 2 frequencies, 2 polarisations CSIRO. CABB, The Instrument

  8. Screened room What’ different: • Just about everything • Frequency and time distribution rebuilt • Optical fibre network reterminated • Old Delay Unit and ATCORR gone • CABB DSP racks installed • Filterbanks • Fringe stopping • Correlation • Integration • Beamforming (Tied Array) CSIRO. CABB, The Instrument

  9. Old AT Correlator CSIRO. CABB, The Instrument

  10. What was hidden under the old AT Correlator CSIRO. CABB, The Instrument

  11. The CABB Correlator CSIRO. CABB, The Instrument

  12. Connections in the CABB Correlator CSIRO. CABB, The Instrument

  13. CABB System Overview E E E E E E E E O O O O O O O O Antenna Control Building 8GHz 2GHz Pol A Pol A Frequency1 Source 1 f1 Pol B CA0n IF Signals Unit 1 Integrated Products ~ ~ Pol A f2 Frequency 2 Source 2 Pol B Pol B Unit 2 Pol A Analog Signal ADC e-VLBI Data Pol B Clock Pulse Crossbar “The Correlator” 4Gsps Fast Digital Slow Digital IF Conversion Digitisation Data Transport & Switching Digital Signal Processing System per Antenna Combined Antennas CSIRO. CABB, The Instrument

  14. 9-bit 4Gsps ADC Module CSIRO. CABB, The Instrument

  15. CABB System Overview E E E E E E E E O O O O O O O O Antenna Control Building 8GHz 2GHz Pol A Pol A Frequency1 Source 1 f1 Pol B CA0n IF Signals Unit 1 Integrated Products ~ ~ Pol A f2 Frequency 2 Source 2 Pol B Pol B Unit 2 Pol A Analog Signal ADC e-VLBI Data Pol B Clock Pulse Crossbar “The Correlator” 4Gsps Fast Digital Slow Digital IF Conversion Digitisation Data Transport & Switching Digital Signal Processing System per Antenna Combined Antennas CSIRO. CABB, The Instrument

  16. dt dt dt dt dt dt ~  Fine Delay e-jt Fringe Rotation Pol A Pol A Baseband Channels Zoom Filters Pol B Pol B Integrated Products p/2 SA 0 Coarse Delay Filter Bank Polarisation * SAB * SB * Input Signals (see System Overview) Int Ctrl TDA TDAB Analog Signal Clock, Control Fast Digital TDB Antenna-Based DSP Slow Digital GTP CSIRO. CABB, The Instrument

  17. Pol A Pol A Baseline Processing Pol B Pol B * * * * * * * Correlation Cell Array Ant 1 Integrated Visibilities dt dt dt dt Baseband Channels Int Ctrl AX * * * * * * * * * * * * * * * * * BX 2 2 2 2 2 2 2 2 2 * * * * * * * AY BY Correlation Cell * * Ant 8 CSIRO. CABB, The Instrument

  18. Pol A Pol A Beam Processing Pol B Pol B a11 Ant 1 an2 a12 an1 Ant 2 Baseband Channels Ant 7 an7 Ant 8 a18 an8 Linear/Circular Tied Array Channels Beam 0 Beam 1 Beam n Pol A X RCP Pol A a17 2 2 1 2 2 2 2 2 1 Y LCP Reconstituted IFs Pol B Pol B Synthesis Filter Bank CSIRO. CABB, The Instrument

  19. Time Domain Characteristics What’s Different: 9-bit ADC data, constant gain not constant power 17+17-bit data into final products No clipping or requantising Controlled rounding and aliased noise ADC dynamic range preserved throughout No gain modulation by satellites in antenna sidelobes or sidelobes sweeping transmitters No settling time during mosaics and cals No van Vleck corrections for strong sources >> Linear, time-invariant (LTI) instrument << High Dynamic Range in the Time Domain => Robust against RFI CSIRO. CABB, The Instrument

  20. Conventional XF and FX vs PDFB CSIRO. CABB, The Instrument

  21. Channel Pass Band Response (Linear Plot) CSIRO. CABB, The Instrument

  22. Frequency Domain Characteristics What’s different: • F/X Correlator • Filterbank on each input IF • Splits 2GHz band into 1, 4, 16 or 64 MHz channels • Two interleaved sets of channels, each set having 2048*1, 512*4, 128*16, 32*64 MHz channels • “Square” channel filter shape • Excellent isolation between channels • Wide dynamic range in the frequency domain => robust against RFI CSIRO. CABB, The Instrument

  23. CSIRO. CABB, The Instrument

  24. CSIRO. CABB, The Instrument

  25. Derivation of Zoom Modes Continuum Channels Normal Wideband Mode Interleaved Channels Continuum Channels Zoom Band Simultaneous Continuum and Line Modes High Resolution Line Channels CSIRO. CABB, The Instrument

  26. Correlator Features Four Basic configurations CFB 1M-0k5 CFB 4M-2k CFB 16M-8k CFB 64M-32k Always (i.e. no trade offs) 2GHz continuum Plus 16 zooms Full polarisation Switched autocorrelations and XY Phases Each zoom band has 2048 channels Plus Tied array output for VLBI and spacecraft tracking CSIRO. CABB, The Instrument

  27. More Goodies 16x increase in bandwidth => 4x sensitivity or 16x telescope speed Large fractional bandwidth => opportunity for BWS => reduced number of antenna configurations per image Simultaneous observation of continuum and multiple spectral lines => greater instrument productivity Large fractional bandwidth => direct observation of spectrum curvature CSIRO. CABB, The Instrument

  28. Autocorrelations at 6cm Structure Missing channels CSIRO. CABB, The Instrument

  29. Cross-correlation amplitudes at 6cm CSIRO. CABB, The Instrument

  30. Cross-correlation phases at 6cm CSIRO. CABB, The Instrument

  31. Vis output at 6cm CSIRO. CABB, The Instrument

  32. CSIRO. CABB, The Instrument

  33. Other Changes- largely transparent to the user ACC has a much reduced role in controlling the receivers, IFs, LOs New “pedestal” computers take over much of this functionality Processes moved from CAOBS to CACOR: • Fringe rotation • Delay, phase, amplitude calibration ( the old CACAL) Much larger data files: currently ~3.7MB/cycle = 1.3GB/hour @ 10 sec cycles. CSIRO. CABB, The Instrument

  34. Contact Us Phone: 1300 363 400 or +61 3 9545 2176 Email: enquiries@csiro.au Web: www.csiro.au Thank you ATNF Dick Ferris Project Engineer Phone: 9372 4262 Email: Dick.Ferris@csiro.au Web: www.csiro.au/group ATNF Warwick Wilson Project Leader Phone: 9372 4324 Email: Warwick.Wilson@csiro.au Web: www.csiro.au/group

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