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

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.

Talk of Bill Petrachenko

Talk of Bill Petrachenko

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

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

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

Labor test and real observation: Use SH25M and TM65 2 hours test observation in July to check functions of CDAS2 Flux (@ X band): 4C39.25 10.0Jy 0902+490 0.27 Jy SNR (Int. Time 2.048 s): 34.2 for 0902+490 1122.6 for 4C39.25

CDAS-2 in the rack Team Leader: Zhu Runji

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

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

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

Ang Project Leader: Dr. Wang Guangli

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

RFI Measurements at Sheshan 1-2GHz

2-4GHz

4-8GHz 8-12GHz

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.

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

Hybrid, FPGA used as HPC, others with PCs

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

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

Thanks!