星载铯原子钟用高精度频率合成器设计

Design of Spaceborne Cesium Atomic Clock with High Precision Frequency Synthesizer

铯束管是一种复杂电真空器件,为了实现原子鉴频功能,需要外部电路提供频率为9192.631770 MHz的信号激励铯原子跃迁。设计了一种铯原子钟用精确频率合成器,利用DDS原理具有非线性输出特性“AD9858+滤波器”的电路结构,以80 MHz频率信号作为参考信号、输出频率为87.36823 MHz的中频信号,供锁相环产生激励铯原子跃迁频率的尾数频率。合成器电路结构简单、体积小,控制参数方便计算,在保证输出信号质量的同时,实现了频标电路频率源的小型化。同时,满足星载铯原子钟在空间环境下正常工作的要求,在真空环境下具有良好的电性能和温度特性。该设计已经成功应用于星载铯原子钟,经过长期在轨测试,采用本文提出的高精度频率合成器设计的星载铯原子钟的准确度为-1.52×10^(-12),满足指标要求。

Cesium beam tube is an electrical vacuum device used as atomic frequency discriminator,which requires an external circuit to provide a frequency signal of 9192.631770 MHz to excite the cesium atom transition.In this paper,a precision frequency synthesizer is designed,which makes use of the characteristics of the DDS principle of nonlinear output.It used the AD9858 with filter circuit structure,to achieve the output frequency of 87.36823 MHz while the 80 MHz frequency signal as a reference signal.The intermediate frequency signal is used for the phase-locked loop to generate the mantissa frequency that excites the cesium atom transition frequency.The circuit has the advantages of simple structure and small volume,and the control parameters are easy to calculate while ensuring the output signal quality.At the same time,it can adapt to the space environment requirements of the space-borne cesium atomic clock,and it has good temperature performance in vacuum environment.The design has been successfully applied to the spaceborne cesium clock.After long-term on orbit test,it can be seen that the accuracy of the spaceborne cesium clock is-1.52×10^(-12)with the frequency design of the high-precision frequency synthesizer proposed in this paper.