NTSC的双混频时差测量系统试运转结果分析

中国科学院国家授时中心(NTSC)新进口的由德国Timetech公司制造的双混频时差测量系统(dual mixer time difference system,DMTD)已经通过了试运行。介绍了DMTD的工作原理和设备结构。NTSC时频基准实验室的主钟(MC)信号作为DMTD的频率参考信号,5个氢钟和18个铯钟的频率信号作为被测信号与MC信号进行相位比对。用频率分配放大器输出的多路MC信号也作为被测信号用以监测DMTD本身的精度和稳定度。给出了DMTD和时间间隔计数器TIC实际测量结果的比较及误差分析。测量结果表明DMTD特别适用于频率短期稳定度非常高的氢原子钟这样的频标之间的频率和时间比对。该设备将用于NTSC的守时工作,不久的将来也将用于铯喷泉与氢钟的频率比对。

Test Running and Data Analysis on the Dual Mixer Time Difference System at NTSC

The newly imported dual mixer time difference system(DMTD) manufactured by Timetech Company has been tested.The operating theory and the structure of the device are described.The frequency signal of the master clock(MC) at NTSC Standard Time and Frequency Laboratory is used as the reference and the frequency signals output of 5 hydrogen masers and 18 cesium frequency standards are fed to the ports of the DMTD for phase comparison with MC.The signals out of a frequency distribution amplifier the input of which is the frequency signal of MC are used to test the measuring precision and frequency stability of the DMTD.The comparison between using DMTD and using the time interval counter,SR 620,is given.The measured time difference fluctuations between MC and each of the clocks show that it is better to use such kind of measuring system for the time difference measurement between hydrogen masers.The DMTD will be used for time keeping at NTSC time lab and for the frequency comparison between hydrogen masers and a cesium fountain in the near future as well.