一种铷原子频标频率综合器新方案的设计与实现

Design and Implementation of a New Frequency Synthesizer for Rubidium Atomic Frequency Standard

数字化和小型化是铷原子频标(RAFS)发展的重要方向.在传统铷原子频标电路中,6 840 MHz微波信号与频率综合器产生的5.312 5 MHz信号进行混频,得到用于激励铷原子跃迁的6 834.687 5 MHz微波探寻信号.早期铷频标的频率综合器大量使用了分立的模拟器件,数字化程度低、参数优化工作繁杂、电路体积较大.目前常用直接数字频率合成器(DDS)方案直接产生5.312 5 MHz信号,但这种数字电路方案通常需要对10 MHz信号进行倍频,它存在频谱纯度较低、相位噪声高等缺点.本文介绍一种产生5.312 5 MHz信号的频率综合器解决方案,这种设计方案在应用DDS器件时无需使用10 MHz倍频电路,它具有频谱纯度较高、相位噪声低、输出频率和相位可调等优点.

Progresses have been made in the development of digitalized and miniaturized rubidium atomic frequency standard(RAFS).In the traditional RAFS circuits,the6840MHz microwave signal is mixed with the5.3125MHz signal generated by the frequency synthesizer to obtain6834.6875MHz microwave signal,which is used to excite rubidium atom transition.Early RAFS frequency synthesizer used a large number of discrete analog devices,and showed disadvantages such as low degree of digitization,complicated parameter optimization and large physical size.The direct digital synthesizer(DDS)scheme used currently generates the5.3125MHz signal directly,but often needs to multiply the10MHz signal.It has the disadvantages of low spectral purity and high phase noise.This paper introduces a digital frequency synthesizer solution that generates the5.3125MHz signal.The design eliminates the need for a10MHz multiplier circuit when using a DDS device.It has the advantages of high spectral purity,low phase noise and adjustable output frequency/phase.