Universal Digital Signal Processing System for Radio Telescopes

D. A. Marshalov, S. A. Grenkov, N. Ye. Koltsov, L. V. Fedotov

Transactions of IAA RAS, issue 71, 9–17 (2024)

DOI: 10.32876/ApplAstron.71.9-17

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

Abstract

For radio astronomy observations, radio telescopes with different diameters antennas are used, for example, RT-32 and RT-13 of the Quasar VLBI Network. These radio telescopes are equipped with various scientific equipment used for observations: highly sensitive radio astronomical receiving systems designed for different frequency ranges and intermediate frequency bands, data acquisition, processing and recording systems. To operate as part of a radio interferometer with very large bases (VLBI) for RT-32 radio telescopes, narrow-band semi-digital signal processing systems R1002M have been developed and are still used, for RT-13 wide-band digital systems are used. Radiometric and spectral observations are carried out using specially designed digital registration systems. The IAA RAS has developed the Multifunctional Digital Backend (MDBE) system based on programmable logic integrated circuits (FPGAs) and high-speed analog-to-digital converters. This made it possible to design a universal digital signal processing system for radio telescopes on its basis. The operating range of the system in 0 - 2 GHz ensures compatibility in the ranges of intermediate frequencies, and the availability of up to 12 broadband channels allows you to independently process signals from the outputs of radio astronomy receivers. The possibility of recording signals in wide bands of 512, 1024, or 2048 MHz increases the sensitivity of the radio telescope, and in the case of using small-diameter antennas, it makes it possible to maintain a signal-to-noise ratio acceptable for observations. The registration mode of 16 independently tunable narrow-band (0.5–32 MHz) frequency channels within the operating frequency band provides interfacing with the existing systems, making it possible to set special settings, as well as providing the possibility to make spacecraft and satellite observations. The standard data format and 10/40GE output interface make it possible to interface with any data recording and buffering systems. The created system is capable of operating in the modes of radiometric registration and spectral observations. It is suitable for any radio telescope, regardless of the size of the antenna and the type of radio receiving equipment, it is able to replace all signal processing equipment on the radio telescope and ensure their registration of data from most radio astronomical observations. Experimental prototypes of the developed system have been installed on the RT-13 and RT-32 radio telescopes at the Svetloe and Zelenchukskaya observatories and are already participating in various radio astronomical observations. The paper summarizes the results of the developing of a universal digital system for radio telescopes. The parameters and variants of the system are given. Algorithms and FPGA configuration for all operating modes of the system are considered. Some results of its use on radio telescopes are presented.

Citation