脉冲激励氢原子钟伺服系统设计

Feasibility of inducing Ramsey interference by pulsed microwave in hydrogen maser was studied. Key parameters were theoretically determined, and a pulsed microwave signal generator was designed. The Ramsey interference of hydrogen atoms was induced successfully on the physical package of a traditional passive hydrogen maser. Line width of the hydrogen atomic transition was reduced to 1.2 Hz from 3.0 Hz. It is expected that the frequency stability of passive hydrogen maser could be improved further by using the design.. The designing of digital servo circuit is in plan. It processes the relaxation signal to produce corrective voltage with Proportional-Integrating-Differential (PID) algorithm. Proper circuits and parameters could be obtained through theoretical analysis and experimental research. A closed control loop will be formed to lock the frequency of voltage-controlled crystal oscillator (VCXO) to the centre peak of the Ramsey fringe and lock the frequency of cavity to the the frequency of VCXO. Then the pulse microwave hydrogen clock will be formed and its frequency stability will be tested. What’s next is to optimize the parameters of the pulse and the system so as to improve the frequency stability of the passive hydrogen maser effectively．

上海天文台时间频率技术研究室开展了利用Ramsey干涉现象设计被动型氢原子钟的可行性研究。该方案的核心是用脉冲微波激励氢原子发生共振跃迁。通过理论计算确定了关键参数，研制了脉冲微波发生电路。利用现有的被动型氢原子钟的物理部分，成功观察到氢原子共振跃迁的Ramsey干涉，将原子跃迁谱线宽度从原来的3 Hz压缩至1.2 Hz。这为进一步提高被动型氢原子钟的稳定度指标提供了一种新思路。.计划设计伺服电路，对氢原子的弛豫信号进行PID运算，得出晶振和谐振腔的纠偏电压，通过理论分析和实验测试，选择合适的电路和参数，将晶振频率锁定在Ramsey条纹的中心峰上、谐振腔频率锁定在晶振频率上，实现整机锁定并测量稳定度指标，最终通过参数的优化将Ramsey干涉引起的线宽压窄效应反映在氢原子钟稳定度性能的提高上。