Multifunctional Digital Backend for RT-13 Radio Telescope at Svetloe Observatory

D. A. Marshalov, E. V. Nosov, L. V. Fedotov, Yu. S. Sheinman

Transactions of IAA RAS, issue 56, 39–47 (2021)

DOI: 10.32876/ApplAstron.56.39-47

Keywords: radio telescope, VLBI, data acquisition system, digital signal processing

Abstract

The RT-32 and RT-13 radio telescopes of the Quasar VLBI Network use various equipment for single-dish, radiometric and spectral observations. The Data Acquisition Systems (DAS) currently used for VLBI on RT-32 radio telescopes at the Svetloe, Zelenchukskaya and Badary observatories are narrow-band and do not fully meet the modern requirements for the frequency bands of the recorded signals. The broadband DAS used on the RT-13 radio telescopes at the Badary and Zelenchukskaya observatories do not have sufficient functionality necessary to meet modern VGOS requirements. To solve these problems, the IAA RAS has developed the Multifunctional Digital Backend (MDBE) that can replace all the variety of DAS and other output devices used on RT-13 and RT-32 radio telescopes. The system contains up to 12 channels, or Digital Signal Processing units that capture the signals from receivers in the 2 GHz band, make required processing with them depending on the type of observation being performed, and send the result to the recording system. The MDBE is controlled from the central computer of the radio telescope and is interfaced with any RT-32 and RT-13 radio receiving systems. The total rate of the information data stream produced by the MDBE and transmitted via optical lines can reach 96 Gbit/s. A block diagram and a description of the hardware of the system, a table of the main parameters of the MDBE, photos of the units included in it, which are built on the basis of programmable logic integrated circuits (FPGAs), are given. The functions performed by the MDBE are determined by the firmware loaded into the FPGA. The structure and description of the FPGA firmware for the Digital Signal Processing unit, which ensures the operation of the system in the VLBI mode, is given. The description of the module operation in this mode is given. The functions of software blocks that provide digital signal processing and analysis, as well as synchronization, control and management of the system are considered. MDBE is installed inside the elevation cabin of the radio telescope. A description and photo of the constructive design of the MDBE are given. The design features of the system and the measures taken to stabilize the temperature regime of its operation are noted. The operation of the MDBE prototype installed on the RT-13 at the Svetloe observatory confirmed its parameters and compatibility with any other existing DAS.

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