integration of the mk5b playback system into the mk4 correlator roger cappallo mit haystack...
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Integration of the Mk5B Integration of the Mk5B Playback System into the Playback System into the
Mk4 CorrelatorMk4 Correlator
Roger CappalloRoger Cappallo
MIT Haystack ObservatoryMIT Haystack Observatory
Concepcion 2006.1.10Concepcion 2006.1.10
+ Additional Haystack Team + Additional Haystack Team MembersMembers
• John Ball
• Kevin Dudevoir
• Mike Titus
• Dan Smythe
• Alan Whitney
• Brian Fanous
• Peter Bolis
New CapabilitiesNew 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
Station Unit ProblemsStation 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
Enhanced PhaseCal CapabilityEnhanced 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)
Integration PlanIntegration 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
Successful Fringes!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
Mk5A to “Mk5B” GGAO - Westford Fringes
Converted Westford raw data file from Mk5B to Mk5A format in software, prior to correlation
Mk4 Correlator Block Diagram
SU
MK5B/DOM
MK5A
VLBA/MK4
TAPE
Mk4Correlator
SUIM
CIBVSI
DTX
DTX
RX
DTX
RX
DTX
RIB
DRX
TSPM
DRX
RIB
RIB
RIB
SU
SUIM
DTX
DTX
RX
CLKM10 MHz
32 MHz
x32
DRX
DRX
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Current Testing StatusCurrent 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
Future PlansFuture 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