The CVN Real Time Correlator Zhang Xiuzhong, Chen Zhong Shanghai Astronomical Observatory China 4th e-VLBI Workshop Sydney

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 1 Gbps from station to Urmuqi New station A New Correlator 2006 New station Fiber in late 2005 – plan 1 Gbps

Main Specification of Chinese VLBI stations NameLocationAntenna diameter (m) Band (GHz) VLBI Terminal Network Connect (Data Rate) Available SheshanNear Shanghai 250.3, 1.6, 2.3, 5.0, 8.4, 22 VLBA, MKIV,S2, MKV No (1) 1987 NanshanNear Urumqi 250.3, 1.6, 2.3, 5.0, 8.4, 22 MKIV, K4, MKV 2Mbps (2) 1994 Mobile VLBI Kunming 32.3, 8.4 S2, MKIV2Mbps (2) 1999 Kunming 402.3, 8.4 MKIV, MKV2Mbps (2) 2006 MiyunNear Beijing 502.3, 8.4 MKIV, MKVNo (2) 2006 (1)100Mbps data rate network connect will be created before end of 2005 (2)10Mbps data rate network connect will be upgrade before end of 2006

Nanshan (Urumqi) at sunrise Seshan (Shanghai)

Main Characteristics : 1. 5 Stations 2. date rate ： Msamples/s, 1 or 2 bits/sample 3. IFs: 8. (16 MHz / IF, may be expanded to 0.5GHz/IF) 4. Integration Time ： 10 ms – 2 hours 5. data format: VLBA 、 MKIII 、 MKIV 、 VSI 6. data source ： Disk Array, Network 7. Functions ： Fringe searcher, Phase Cal 8. Output: via net and disk files ( in FITS format) CVN Real Time Correlator

Architecture of Correlator (Chinese Lunar Project)

Data Stream & PBI

Diagram of PBI

FFT Module

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.

Virtex-II FPGA chips PBD(CVNHD)

Some Results of Real Time Correlator The Fringe of the SH-UR Baseline TC-1 observation with Integration time of 4 seconds The Fringe of the SH-UR Baseline TC-1 observation with Integration time of 62.5 ms

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

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.

MKV – PBD – Correlator

PBD Data Flow

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

The Future plan 1. MKV connection via network 2. Network creation 3. System auto-operation software developement

The network connect

Thank you