An Open-Source VLBI Digital Backend for Low-Cost FPGA-based SoCs

Very Long Baseline Interferometry (VLBI) techniques have become crucial in radio astronomy and geodesy due to the major improvements that they provide to the observations, outcomes, at the expense of requiring a significant computational load to implement the corresponding processing in real time. The devices responsible for these digital signal processing tasks in the application field, mainly based on Field-Programmable Gate Arrays (FPGAs), are known as Digital Backends. Currently, the costs coming from the state-of-the-art digital backends are high and their FPGA designs either require expensive software licenses to be involved, or they are released as proprietary solutions. This work proposes a novel SoC (System-on-Chip) architecture, based on a Xilinx Zynq device, for a digital backend focused on VLBI applications. The architecture is capable of managing the acquisition stage at the required data rates, and packing data in the well-known VDIF format to upload them. By offering a low-cost open-source architecture, it becomes a suitable solution for dissemination purposes, as well as for specific research fields. Furthermore, the system has been successfully validated with its implementation and test in some preliminary experimental setups.