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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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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


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



Nanshan (Urumqi) at sunrise

Seshan (Shanghai)


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)


Architecture of correlator chinese lunar project
Architecture of Correlator(Chinese Lunar Project)





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.


PBD(CVNHD)

Virtex-II FPGA chips


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


MKV Connection Integration time of 4 seconds

  • 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


Transfer mode in Low rate Integration time of 4 seconds 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.


Mkv pbd correlator
MKV – PBD – Correlator Integration time of 4 seconds


PBD Data Flow Integration time of 4 seconds


Test Results Integration time of 4 seconds

  • 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


The Future plan Integration time of 4 seconds

  • MKV connection via network

  • Network creation

  • System auto-operation software

  • developement


The network connect Integration time of 4 seconds


Thank you

Thank you Integration time of 4 seconds 


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