中文摘要：

为提高云南天文台40m射电望远镜射电源流量观测性能，针对S波段现有问题，设计并研制了一套流量观测系统。研发硬件包括抗干扰射频模块、K因子辐射计。同时开发了与新系统配合工作的观测软件，用于数据采集、实时显示、储存及处理。系统研制完成后，进行了安装测试。测试方式为河外致密源ON／OFF流量观测。观测结果表明，实测灵敏度接近理论值水平，新研制系统性能较旧设备有显著提高。

英文摘要：

To improve the capability of the YNAO 40m telescope, we have developed a new S-band flux measurement system to solve the known problems. The newly developed devices include a counter-interference RF module and a radiometer for K-factor measurement. A new observation software is also introduced to match the system. The software is used for data collection, real-time data display, data recording/reduction. We have carried out certain tests after the new system was installed. The ON/OFF observation mode for a point source was adopted. The results after the data reduction and analysis show that the observational sensitivity of our new system is close to the theoretical value. The new system has obvious improvement over the old system in use with the telescope.