DAC采样时钟杂散对载波信号短期频率稳定度影响研究  

Influence of DAC sampling clock spur on short-term frequency stability of carrier signal

作　　者：秦晓伟[1] 杜二旺[1] 王国永[1] 何冬[1] QIN Xao-wei;DU Er-wang;WANG Guo-yong;HE Dong(China Academy of Space Technology（Xi＇an）,Xi＇an 710000,China)

机构地区：[1]中国空间技术研究院西安分院,西安710000

出　　处：《时间频率学报》2018年第3期214-218,共5页Journal of Time and Frequency

摘　　要：频率稳定度作为评估卫星钟性能的一个重要指标,它直接影响着卫星导航、定位、授时的精度。在DAC(digital to analog converter)实现模拟化过程中,利用非理想采样时钟对230kHz载波信号进行采样,然后利用FFT(fast Fourier transformation)实现对采样后载波信号的鉴相,最后根据鉴相结果计算载波信号的短期频率稳定度。通过仿真分析可知,DAC采样时钟上的"毛刺"不仅作为载波信号的调制信号,而且其功率和频率都会影响载波信号的短期频率稳定度。当杂散功率确定情况下,杂散信号频率靠近载波信号频率时,载波信号的短期频率稳定度变差;当杂散信号频率远离载波信号频率时,载波信号的短期频率稳定度变好。当杂散频率确定的情况下,杂散信号功率相对于载波信号功率越小,载波信号的频率稳定度越好。Frequency stability is one of key index for assessing performance of satellite clock, which directly affecting accuracy of satellite navigation and positioning, as well as timing service. In the process of simulation of DAC（digital to anabg converter） ,the carrier signal with 230 kHz frequency is sampled by non-ideal sampling clock,and then the phase error 1oetween reference signal and sampled signal is obtained by using FFT （fast Fourier transformation） algorithm. Finally, short term frequency stability can be calculated according to the results of phase detection. The simulation analysis showed that the spurs of DAC sampling clock was modulated lay the carrier signal, and it generated spurious in the output signal, also the short term frequency stability of carrier signal was affected lay its power and frequency. When the stray power is determined, the short term frequency stability got worse while spurious signal frequency closed to carrier signal frequency. While spurious frequency was determined , the smaller of the power of spurious signal with respect to the power of carrier signal,the 1oetter of the short term frequency stability of carrier signal was.

关 键 词：卫星钟 杂散信号 频率稳定度 采样时钟 

分 类 号：TN967.1[电子电信—信号与信息处理] TM935.115[电子电信—信息与通信工程]