TM65 m射电望远镜Ku、K、Ka和Q频段天线性能测量

Antenna Performance Measurements in Ku, K, Ka,and Q Bands for the TM65 m Radio Telescope

讨论了TM65m射电望远镜Ku、K、Ka和Q4个高频段天线效率、灵敏度以及系统噪声温度的性能测量工作.首先介绍了TM65m接收系统4个高频段的关键指标,接着对测量工作中需要注意的方面进行了论述,主要包括望远镜指向和副面位姿模型的构建、噪声源的定标以及大气的影响.最后给出了TM65m在这4个频段的天线效率、灵敏度以及系统噪声温度的实测结果.测量结果表明:在最佳俯仰角45°-65°范围内,Ku、K、Ka和Q4个波段天线效率均可以达到约50%,而在较高和较低的俯仰角上,由于主面变形的缘故,效率有明显的下降现象.当俯仰角为50°左右时,4个波段的灵敏度分別为38 Jy、120 Jy、200 Jy和110 Jy.

The critical performance indicators of the TM65 m radio telescope are described. We report the antenna efficiency, sensitivity, and system noise temperature performance measurements in Ku, K, Ka, and Q bands. The key indicators of the four bands＇ receiving systems are introduced firstly. The issues which are critical to the measurements are discussed. These include pointing, sub-reflector model, noise diode calibration, and the atmosphere. The current antenna efficiency, sensitivity, and system noise temperature of the four bands are reported. The measurement results show that 50% efficiencies can be achieved in all four bands at the mid-point of the elevation range. Currently, at higher and lower elevations, there is a significant decline in the efficiency as a result of the main surface deformation with elevation. The sensitivities of the four bands in the mid-elevation about 50° are 38 Jy, 120 Jy, 200 Jy, and 110 Jy, respectively.