BPL工作钟信号T(PU)的监控方法研究

Research on the Methods for Monitoring and Controlling BPL Working Clock

中国科学院国家授时中心(NTSC)BPL长波授时台升级改造项目要求实现BPL系统的工作钟信号T(PU)的自动监控。T(PU)的控制指标为T(PU)与NTSC时频基准实验室的主钟信号UTC(NTSC)之间的相位时间差的绝对值|UTC(NTSC)-T(PU)|小于50 ns; T(PU)的频偏绝对值优于5×10^(-13)。为达到上述指标,并尽可能提高T(PU)的准确度,研究了在采用不同类型的原子钟作为工作钟频率源时所需采用的T(PU)的监控方法。结论是对日稳较好的频率源,用对工作钟频率源的频偏进行准实时预报得到的值和实测得到的相位时间差UTC(NTSC)-T(PU)来计算应该加到相位微调仪上的频率补偿值,从而进行工作钟的频率驾驭,可以大大提高工作钟信号T(PU)的准确度;而对不太稳定的频率源,频偏准实时预报准确度很差,采用几个月时间段内的平均频偏以及实时实测的相位时间差来进行频率驾驭,以便确保T(PU)的准确度。

The requirement for automatically monitoring and controlling the BPL working clock signal T（ PU ）has been requested by the renovation project of the Long Wave Time and Frequency Broadcasting System （ BPL ） at National Time Service Center （ NTSC ）, the Chinese Academy of Sciences. The specifications for the T （PU）controlling must achieve the absolute phase time difference, ｜UTC （NTSC） - T （PU）｜, smaller than 50 ns, where UTC （ NTSC ） is the master clock signal generated by the Standard Time and Frequency Laboratory of NTSC and the absolute frequency offset of T （ PU ） 〈 5.0×10^-13. In order to reach the specifications and improve T （ PU ） as accurate as possible, the methods for monitoring and controlling T （ PU ） are discussed for several different kind of atomic clocks, which are used as the frequency sources of the working clock. AS a result, for the atomic clocks with better short term （ τ- 1 d ） frequency stability, which is used as the frequency source of the working clock, the quasi-real time predicted frequency and the measured phase offset between UTC （ NTSC ） and T （ PU ） can be used to calculate the frequency compensation that should be set on the micro-phase stepper to realize the working clock frequency steering, so as to greatly improve the accuracy of T （ PU ）. For the atomic clocks, used as frequency sources, with worse short term frequency stability, the quasi-real time predicted frequency is far from accurate as needed, so the averaged frequency offset of a few months as well as the real time measured phase time difference can be used for the frequency steering in order to meet the controlling specification.