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Integration of the Mk5B Playback System into the Mk4 Correlator

Integration of the Mk5B Playback System into the Mk4 Correlator. Roger Cappallo MIT Haystack Observatory Concepcion 2006.1.10. + Additional Haystack Team Members. John Ball Kevin Dudevoir Mike Titus Dan Smythe Alan Whitney Brian Fanous Peter Bolis. New Capabilities.

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Integration of the Mk5B Playback System into the Mk4 Correlator

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  1. Integration of the Mk5B Playback System into the Mk4 Correlator Roger Cappallo MIT Haystack Observatory Concepcion 2006.1.10

  2. + Additional Haystack Team Members • John Ball • Kevin Dudevoir • Mike Titus • Dan Smythe • Alan Whitney • Brian Fanous • Peter Bolis

  3. New Capabilities • Increased correlator throughput • 32 MHz playback independent of record rate (if desired) • Inter-scan gap of ~5-10 seconds • Increased reliability over SU • SU has 17 x 6U boards → 1 FPGA chip • Xilinx code rigorously simulated • Much simpler software than in SU • Flexibility in FPGA design • 16 tone x 16 channel phase cal • ½ speed 2 Gb/s playback

  4. Station Unit Problems • Byte slips at 32 MHz playback rate causing amplitude loss • Amplitude loss proportional to parity error rate • Intermittent large pcal values • Intermittent loss of fringes • Intermittent crashes • Slow (~30 s) sequencing for scan setup

  5. Enhanced PhaseCal Capability • 16 tones (cf. 2 in SU) in each of 16 channels with 99.6% duty cycle • Response to spurious signals > 40 dB • Sinewave x data product has 128 levels (cf. 4 levels in SU) with 1/256 rot phase quantization (cf. 1/16 rot)

  6. Pcal Rotator Representation

  7. Integration Plan • Rigorous standalone testing of Mk5B via simulation and test vectors • Testing of data acquisition using DIM, and building on Mk4 capability • Tests of DOM in SU mode using canonical data for which the answers are known via Mk4

  8. Successful Fringes! • GGAO to Westford test scan on a geodetic source • GGAO recorded in Mk5A format • Westford sampled and recorded using Mk5 sampler module (Mk4 formatter + VSI4 board) • Westford data file then converted by standalone “b2a” program to be Mk5A VLBA format (an easy conversion) • Standard Mk4 correlation using 2 MK5A’s

  9. Mk5A to “Mk5B” GGAO - Westford Fringes Converted Westford raw data file from Mk5B to Mk5A format in software, prior to correlation

  10. Mk4 Correlator Block Diagram

  11. Mk5B Interfaced to Mk4 Correlator

  12. Current Testing Status • Messaging system working cross-platform • Correlator run-time software functional • Mk5B controller software has most of needed functionality: • Initialization, mounting, scan-seek, header-read all working • ~1 week of additional coding needed

  13. Future Plans • Incorporation of 16 tone phase cal into fourfit • Statistical robustness to tone contamination • Phase corrections across band to increase sensitivity • Derive single-band delays per channel from multiband delay + pcal-derived channel delays • should result in better coherence across channels. • estimate only multi-band delay and delay rate • Expansion of the Mk4 correlators • 16 stations possible if sufficient # of Mk5B’s • Correlator control computer upgrade to modern PC + Linux

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