Design of VDIF formatter/deformatter and network interfaces for real-time VLBI

Abstract In a very long baseline interferometry (VLBI) system, multiple radio telescopes far apart observe the same radio source simultaneously and then transmit the observed data from digital backends to a correlator. This paper describes a data transmission system designed for the digital backends and the hardware correlator based on field programmable gate array (FPGA), which can support real-time VLBI (e-VLBI) observations with the existing Internet. The data transmission system includes four parts: the VLBI data interchange format (VDIF) formatter, the network transmission interface, the VDIF deformatter and the network receiving interface. Where, the first two parts are embedded in the digital backends, while the latter two parts are embedded in the hardware correlator. Experimental results and real observations demonstrate that the functions of the VDIF formatter/deformatter are correct, and the throughput performance of the network transmission/receiving interfaces can meet the requirements of use.