A Study of Evaluation of Electromagnetic Radiation Levels of Electronic Devices Near a Radio Telescope

An astronomical radio telescope has extremely high system sensitivities. With increasingly amounts of digital high-speed back-ends and control modules in radio telescopes and intensifying external radio interferences for observational stations, electromagnetic environments of astronomical radio telescopes are increasingly deteriorating. Detailed evaluations of electromagnetic radiation levels of electronic devices affecting radio telescopes can provide important guidance for the electromagnetic compatibility to be considered in design and system improvement of radio telescopes. In this paper we use a simple approach to analyze system sensitivities of telescopes and the relevant assessment criteria of electromagnetic radiation levels of electronic equipments in radio astronomy. We then give a method to calculate side-lobe gains of radio antennas. We further propose a method to evaluate influences of electromagnetic radiations of telescope equipments on observations in radio astronomy. We have calculated the allowed interference limits of the 25m radio telescope at the Nanshan Station of the Xijiang Astronomical Observatory based on system sensitivities and observational requirements of the telescope. Using the calculated interference limits and the method for side-lobe gains in data processing and emission-level evaluation, we have measured the radio spectrum of radiation from the antenna drive system of the 25m telescope. The results lead to the required shielding-effectiveness values of the antenna drive system. The values can be rather helpful for designing the shielding apparatus to mitigate interferences of the antenna drive system.