ZHAO Wen-yu1,2，JIANG Hai-feng1，ZHANG Shou-gang1,2

（1. National Time Service Center, Chinese Academy of Sciences, Xi’an, Shaanxi,710600, China;

2. Graduate University of Chinese Academy of Sciences, Beijing 100039, China）

Abstract：The cesium atomic fountain clock is the time and frequency primary standard. The noise quality of the frequency synthesizer impacts the stability performance of the atomic fountain clock directly. The design and implementation of a low noise frequency synthesizer used for cesium atomic fountain clock are presented. The tests on the frequency synthesizer indicate that the measured phase noise of the output signal at 9.2 GHz is －82dB[Rad2/Hz]@offset1Hz,which satisfies the demands of the design.

Key words：cold atomic fountain clock；frequency synthesizer；phase locked loop