The Design And Application Of A Receiver Noise Source Control System

Noise source is an important part of radio astronomy receiver system. Every receiver system contains a noise source, which has been calibrated. Noise source is a ruler. The receiver noise temperature can be calculated by noise source. The terminals are mainly used for processing and storing the received radio astronomy data, including the data of noise injection. The noise source is controlled by the terminal. For different astronomical observations, the time of noise injection, the length of time for noise injection and the noise level are determined by the observational program.Usually a terminal is only used for one astronomical observation subject, but an astronomical observation subject needs different receivers. So every terminal needs to control multiple receiver noise sources. Therefore, it needs a special equipment to connect the terminal and the receivers, which responses for switching and transforming the control signal of different terminals. In this paper the special equipment is designed to control the noise source.This topic is part of the project named Phase Corrector Development and The Noise Source Control, which is the subproject of the renovation project of Nan Shan 25m telescope. This paper mainly completes the control system design and application of receiver noise source. All terminals’ control signal is converted into a unified differential signal. Signal links are controlled by CAN bus which is making connection between terminals and receiver noise sources. In this design there are two units. One is in the observation room, which is used for switching signal among different terminals. Another is in the high frequency bin, which is used for switching the control signal of noise sources. The control system of receiver noise source realizes all design functions, including signal transforming, switching and controlling. Now it has been successfully applied in the astronomy observation.