1. The Development of Broadband VLBI Technologies in SHAO
Xiuzhong ZHANG
Shanghai Astronomical Observatory, CAS
3rd International VLBI Technology Workshop , JIVE
10-14 Nov. 2014

2. Following VLBI 2010 project, SHAO started to study broadband VLBI tech.
There are several groups working on the broadband VLBI tech. in SHAO
After long time discussion, SHAO decided to build a VGOS station by self-raised funds at Sheshan, near Shanghai.
This decision push SHAO engineers to work on the broadband VLBI tech.

3. Talk of Bill Petrachenko

4. Talk of Bill Petrachenko

5. Cryogenic Front End One set QRFH and LNA from Caltech
Design and develop Cryogenic system with cooperation of industry
Study the measurement methods of performance of broadband cryogenic receiver
Low Noise Amplifiers
Replace with photos

6. Prototype System of UDC
Up Down Converter
Many companies are interest to help us to develop UDC for our VGOS station
Main specification:
Input : 2 – 14GHz (with linear polarizations)
Output: 512~1024 / 70 ~ 1024MHz selectable
Programmable with 0.1 MHz step
Prototype System of UDC

8. CDAS-2
With the new platform, CDAS2 with PFB (Poly-phase Filter Bank) algorithm is under testing. Now it can work in two modes:
512 MHz Dual IF Mode:
For each IF, it has
– 512 MHz bandwidth input
– 16 channels output
– 32 MHz bandwidth for each output channels
1024 MHz Single IF Mode :
– 1024 MHz bandwidth input
– 64 MHz bandwidth for each output channels

9. Labor test and real observation:
Use SH25M and TM65
2 hours test observation in July to check functions of CDAS2
Flux X band):
4C Jy Jy
SNR (Int. Time s):
34.2 for
for 4C39.25

10. CDAS-2 in the rack
Team Leader: Zhu Runji

11. MK6 Disk Array Two set MK6 system are already arrive in Shanghai
Doing test with CDAS-2 now

12. Calibration and time System
Pcal, Tcal and Dcal are in developing
Time/Frequency: shared with current system
Meteorological system: shared with current system

13. Main Specifications of Antenna
Diameter: 13m
RF frequency range: 2-14GHz, upgradable to Ka band
Polarization: Linear polarizations
Optics: Ring focus
Aperture efficiency: >50%
Surface accuracy: <0.3mm
Pointing accuracy：<18”
Slew rate: az 12o/s, 3o/s2 ; el 6o/s, 3o/s2
Slew range: az -270o~+270o; el 0o~90o
Reference point stability: ＜0.3mm
Signal path length stability: ＜0.3mm

14. Ang
Project Leader:
Dr. Wang Guangli

15. Antenna
There are two companies are interest to help us to develop VGOS antenna.
Both of these two companies have capacity to develop VGOS antenna.
SHAO should select one of them and sign antenna contract in near future

16. RFI Measurements at Sheshan
1-2GHz

17. 2-4GHz

18. 4-8GHz
8-12GHz

19. The RFI occurs in S-band
The RFI occurs in S-band. It is difficult to use continues broadband at S-band for VLBI observations. The Superconducting Filter is planned to use for the reduction of the RFI effects.

20. Some Words for Correlator
The way to develop the Correlator :
Platform Selection:
Software, PC based, GPU based
more power consumption,
need high speed inter-connect between PCs
Hardware, FPGA based
need long time to develop the firmware
need more libraries to reduce the developing time
Hybrid, FPGA used as HPC, others with PCs
not so more power consumption
reduce the developing time

21. Hybrid, FPGA used as HPC, others with PCs

22. Correlator Main Spec. (one Uniboard): 4 Stations, 2Gbps/ Station
System Control
Data Buffer (Playback)
Main Spec. (one Uniboard):
4 Stations, 2Gbps/ Station
UniBoard & Power supply
Many thanks for the helps of JIVE and ASTRON UniBoard team!
Team Leader: Xu Zhijun

23. Summary
The electronics part of Sheshan VGOS station will be completed in near future
Sign Antenna contract as soon as possible
Cryogenic Receiver design and development
Improve the performance of UDC and DAS
Broadband test observation with current big antenna
Study of the structure of the Correlator

24. Thanks!