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)

Pcal Rotator RepresentationPcal Rotator Representation

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

texttexttext

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Mk5B Interfaced to Mk4 CorrelatorMk5B Interfaced to Mk4 Correlator

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