基于斩波轮技术的K波段接收机噪声校准研究

Research on K-band Receiver Noise Calibration Based on Chopper Wheel Technology

接收机是射电天文中用于探测微弱射电信号的重要接收设备.接收机的强度校准就是将接收机对射电源的响应转换为天文意义上的流量密度.常规方法就是使用经典的冷热负载法,将接收机自身的强度响应转换为一个等效的温度值,之后再据此对射电源做进一步标定.通过搭建基于斩波轮技术的K波段接收机强度校准平台,使用斩波轮法测试K波段常温接收机的噪声温度,并与传统冷热负载法的测试结果进行比对.结果显示,在晴好天气条件下,斩波轮法在30°、90°仰角下噪声温度的最大测试误差为7.5%和8.4%,可以很好地应用于实际噪声温度测试中;但在5°仰角测试中,由于过低仰角引入了地面噪声,使得斩波轮法的测试误差上升至20%–30%之间而无法使用.希望在此基础上进一步开展K波段天空亮温度的理论计算与实测,从而完善斩波轮技术的应用,使之可以满足在不同气象条件下的噪声校准测试需求.

The receiver is an important device for detecting weak radio signals in radio astronomy.The amplitude calibration of the receiver is to convert the response of the receiver for radio source into the flow density in astronomy.The conventional method is to convert the amplitude response of the receiver itself into an equivalent temperature value using the classical cold and ambient load method,and then further calibrate the radio source.The K-band receiver amplitude calibration platform based on the chopper wheel technology is built,and the noise temperature of the K-band normal temperature receiver is tested by the chopper wheel method,and compared with the test results of the conventional cold and ambient load method.From the results,under the fine weather conditions,the maximum test error of the noise temperature at the 300 and 900 elevation is 7.5%and 8.4%,which can be well applied to the actual noise temperature test;but at the 50 elevation test,the ground noise was introduced due to the low elevation angle,so the test error of the chopper wheel method was increased to about 20%-30%and could not be used.This paper also hopes to further develop the theoretical calculation and actual measurement of the K-band sky brightness temperature on this basis,so as to improve the application of the chopper wheel technology,so that it can satisfy the noise calibration test requirements under different meteorological conditions.