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The CVN Real Time Correlator Zhang Xiuzhong, Chen Zhong Shanghai Astronomical Observatory China 4th e-VLBI Workshop Sydney 2005.7. Outline : VLBI Stations in China The 5 station Real Time Correlator Some results of Real Time Correlator Mark5 connection The Future plan.

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slide1

The CVN Real Time Correlator

Zhang Xiuzhong, Chen Zhong

Shanghai Astronomical Observatory China

4th e-VLBI Workshop

Sydney 2005.7

slide2

Outline :

  • VLBI Stations in China
  • The 5 station Real Time Correlator
  • Some results of Real Time Correlator
  • Mark5 connection
  • The Future plan
vlbi stations in china
VLBI Stations in China

New station - 2006

1 Gbps from station to Urmuqi

Fiber in late 2005 – plan 1 Gbps

A New Correlator

2006

New station - 2006

slide6

CVN Real Time Correlator

  • Main Characteristics :
  • 5 Stations
  • date rate:0 - 256Msamples/s, 1 or 2 bits/sample
  • IFs: 8. (16 MHz / IF, may be expanded to 0.5GHz/IF)
  • Integration Time:10 ms – 2 hours
  • data format: VLBA、MKIII、MKIV 、VSI
  • data source :Disk Array, Network
  • Functions:Fringe searcher, Phase Cal
  • Output: via net and disk files ( in FITS format)
the advantages
The Advantages
  • The correlator has fringe searcher and P-cal access function.
  • The PC-based disk array(CVNHD) will be used as the playback system for correlator. There are maximal 4GB memory should be mounted in these PCs. The 4GB memory could take on a huge FIFO, to smooth the data stream from disk array and from network. The commercial PC board AD7300A is used in these PCs, as a high data rate interface between PC memory and playback interface. The data rate of interface is 10Mbps for real time correlation and 256Mbps for post correlation. The data streams are controled by playback interface.
  • The FFT and MAC logics of one channel of 5 stations could be configured in one FPGA chip. Compared with old hardware correlator, this design could reduce many connect cables and will increase the system reliability.
slide12

PBD(CVNHD)

Virtex-II FPGA chips

slide13

The Fringe of the SH-UR Baseline TC-1 observation with Integration time of 4 seconds

Some Results of Real Time Correlator

The Fringe of the SH-UR Baseline TC-1 observation with Integration time of 62.5 ms

slide14

MKV Connection

  • Transfer Mode:MKV to PBD transfer through network

MKV command : disk2net, in2net

Net protocol : tcp/udp, tcp prefered

  • PBD(CVNHD)

Command : net2mem, mem2card

Net protocol : tcp/udp, tcp prefered

slide15

Transfer mode in Low rate Network Connection

  • Mark5A Disk FIFO Mode(Need more tests)

A special ‘disk-FIFO’ mode use a Mark 5 scratch disk pack as the FIFO buffer in the case network transfer rates are slow. It is suitable for the low network transfer rate (10Mbps) for chinese Lunar Project .

  • Make data in FIFO Disk Pack usable for playback after experiments is to be done in the future.
slide18

Test Results

  • MK5 – PBD in 100Mbps network

Network transfer rate>50Mbps

peak rate~100Mbps

  • MK5 – PBD – 7300A –PBI

A/D 7300A : TRIG_DO_CLK_10M_ACK, 32bits

Average speed 250kbps, controled by PBI

slide19

The Future plan

  • MKV connection via network
  • Network creation
  • System auto-operation software
  • developement
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