Installing a VLBI Digital Backend with DBBC2 at Nanshan Station, Xinjiang Astronomical Observatory

Base Band Converters (BBC) are the key components of Very Long Baseline Interferometry (VLBI) backend. With the rapid development of computer and digital technology, Anolog BBCs (ABBC) have recently been superseded by Digital BBCs (DBBC) in the field of radio astronomy. Compared with ABBC, DBBC have much higher flexibility and support much wider bandwidth recording in VLBI observations. Considering these advantages and the key role of Nanshan station in international VLBI networks, a VLBI digital backend with DBBC2, developed by Hat-Lab (Italy), has been installed at Nanshan station, Xinjiang Astronomical Observatory. The DBBC2 is fully compactible with the European VLBI network (EVN). In the paper, we gave a proper introduction to the new equipment including its structure, key modules, input and output interfaces. We also mentioned how to assemble, connect, configure, calibrate and test the equipment. After all these necessary verifications, we performed some testing observations. Fringes to Nanshan DBBC2 were successfully found in these experiments. These successes indicate that the new digital backend is successfully established and works quite stably at Nanshan station. With the new digital backend, we can achieve a recording rate of 2/4Gbps in the wide-band VLBI observations. This will enable astronomers to image much fainter radio sources with the milliarcsecond resolution.