Local oscillator induced degradation of medium-term stability in passive atomic frequency standards
Local oscillator induced degradation of medium-term stability in passive atomic frequency standards
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发表时间：
1990-05
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通讯作者：
G. Dick;J. Prestage;C. Greenhall;L. Maleki
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作者：
G. Dick;J. Prestage;C. Greenhall;L. Maleki
随着无源原子频率标准性能的提高，由于辅助本地振荡器 (L.O.) 的频率波动，遇到了新的限制。该效应是由于补偿 L.O. 的反馈增益的时间变化造成的。频率波动。新的微波和光学捕获离子标准所承诺的高性能可能会受到这种效应的严重影响。研究人员针对顺序询问标准的情况对这种性能限制进行了分析。询问过程对 L.O. 的敏感性随时间变化。针对单脉冲和双脉冲 Ramsey RF 询问以及调幅脉冲评估频率波动。这些不同的时间依赖性对标准性能的影响是针对 L.O 计算的。频率波动显示出典型的 1/f 谱密度。限制为 1/sq。频率波动的根伽玛相关偏差根据脉冲长度、死区时间和脉冲重叠来计算。研究人员还针对这个问题提出了概念性和面向硬件的解决方案，从而实现了对 L.O. 更加接近恒定的敏感性。波动。解决方案涉及使用双脉冲询问；交替询问多个陷阱，以便一个陷阱的死区时间可以被另一个陷阱的操作覆盖；对两个陷阱使用双脉冲询问，这样在射频脉冲期间，一个陷阱灵敏度的增加往往会补偿另一个陷阱灵敏度的下降。还提出了利用放大调制脉冲的解决方案，其名义上显示零时间变化。
As the performance of passive atomic frequency standards improves, a new limitation is encountered due to frequency fluctuations in an ancillary local oscillator (L.O.). The effect is due to time variation in the gain of the feedback which compensates L.O. frequency fluctuations. The high performance promised by new microwave and optical trapped ion standards may be severely compromised by this effect. Researchers present an analysis of this performance limitation for the case of sequentially interrogated standards. The time dependence of the sensitivity of the interrogation process to L.O. frequency fluctuations is evaluated for single-pulse and double-pulse Ramsey RF interrogation and for amplitude modulated pulses. The effect of these various time dependencies on performance of the standard is calculated for an L.O. with frequency fluctuations showing a typical 1/f spectral density. A limiting 1/sq. root gamma dependent deviation of frequency fluctuations is calculated as a function of pulse lengths, dead time, and pulse overlap. Researchers also present conceptual and hardware-oriented solutions to this problem which achieve a much more nearly constant sensitivity to L.O. fluctuations. Solutions involve use of double-pulse interrogation; alternate interrogation of multiple traps so that the dead time of one trap can be covered by operation of the other; and the use of double-pulse interrogation for two traps, so that during the time of the RF pulses, the increasing sensitivity of one trap tends to compensate for the decreasing sensitivity of the other. A solution making use of amplified-modulated pulses is also presented which shows nominally zero time variation.