1. Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210033;2. Key Laboratory of Radio Astronomy, Chinese Academy of Sciences, Nanjing 210033;
超导SIS (Superconductor-Insulator-Superconductor)接收机因极低的接收机噪声温度成为毫米波和亚毫米波段射电天文观测的首选. 本振系统耦合噪声也是接收机噪声的一部分, 在多年的天文观测中, 发现本振耦合噪声无法完全忽略, 对天文观测的灵敏度有一定影响. 采用两个不同种类的信号发生器作为本振系统初级信号源, 测试了超导SIS接收机的噪声温度, 发现信号发生器输出的基底噪声能够耦合到接收机内部, 从而增加接收机噪声强度. 分析研究了本振系统热噪声和信号发生器基底噪声对接收机噪声的影响. 通过在信号发生器输入端加入窄带滤波器滤除其基底噪声, 消除了信号发生器基底噪声引入的接收机噪声, 降低了接收机的整体噪声, 提高了望远镜的灵敏度.
The Superconducting Superconductor-Insulator-Superconductor (SIS) receivers have become the preferred method for (sub)millimeter-wave radio astronomical observations due to the extremely low receiver noise temperature. The coupling noise of the local oscillator (LO) system is also a part of the receiver noise. In many years of astronomical observations, it is found that the coupling noise of LO can not be completely ignored, which has a certain impact on the sensitivity of astronomical observations. The noise temperature of the superconducting SIS receiver was tested using two different kinds of signal generators as the primary signal source of LO system. It is found that the base noise output by the signal generator can be coupled into the receiver and deteriorate the receiver noise. By adding a narrow band filter to the input of the signal generator, the base noise of the signal generator can be filtered, and this part noise of the receiver can be eliminated, the overall noise of the receiver is reduced, and the sensitivity of the telescope is improved.