基于氢原子钟的频率源无缝切换系统设计
Design of Frequency Source Seamless Switching System Based on Hydrogen Atom Clock

频率源高精度切换技术是许多前沿科学和国家重大科学工程的关键技术，是保证高精度时频系统输出稳定、可靠的时频信号的关键。为实现频率源高精度无缝切换，本文研究并设计了一种基于氢原子钟的频率源无缝切换系统，该系统利用氢原子钟作为被切换的频率源，通过双混频时差测量方法，获得了更高的时差测量分辨率，利用数字锁相方法提高了鉴相精度，在频率源出现故障或者性能下降时，自动实现主、备频率源之间的高精度无缝切换。仿真结果表明：压控振荡器与氢原子钟锁定时，其频率稳定度可以达到10^？13，与未锁定时相比提高了两个数量级，在锁相过程中实时监测频率源的频率稳定度，当氢原子钟出现短时或持久跳变时，可以进行氢原子钟的无缝切换，切换瞬间的时差跳变量处于皮秒量级。
High-precision switching technology of frequency source is the key technology of many frontier sciences and major national scientific projects, and it is the key to ensure the stable and reliable output of high-precision time-frequency system. In order to achieve high-precision seamless switching of frequency sources, this paper studies and designs a frequency source seamless switching system based on a hydrogen atom clock. The system uses a hydrogen atom clock as the switched frequency source, obtains a higher resolution of time difference measurement through the dual-mixing time difference measurement method, and improves the phase identification accuracy by using the digital phase lock method. Automatic high-precision seamless switching between primary and secondary frequency sources. The simulation results show that when the VCO is locked with the hydrogen atom clock, its frequency stability can reach 10^？13, which is two orders of magnitude higher than when it is not locked. The frequency stability of the frequency source can be monitored in real-time during the phase-locking process. When the hydrogen atom clock has a short or persistent jump, the hydrogen atom clock can be seamlessly switched, and the time difference jump variable of the switching moment is in the order of picosecond.