A simple analysis of the Dick effect in terms of phase noise spectral densities
A simple analysis of the Dick effect in terms of phase noise spectral densities
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DOI：
10.1109/58.710552
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发表时间：
1998
期刊：
影响因子：
--
通讯作者：
L. Presti;Daniele Rovera;A. D. Marchi
中科院分区：
文献类型：
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作者：
L. Presti;Daniele Rovera;A. D. Marchi
在基于Ramsey双作用方法的冷原子频标中，询问信号的相位噪声表现为随机的“端到端相位差”，从而在环路中引入了频率噪声。本文利用相位噪声功率谱密度S/sub /spl φ/f（f）在傅立叶频域中分析了这种现象。在连续操作的标准中，由此引入的过量噪声在长期内被伺服消除，以最终变得小于原子散粒噪声，而在具有脉冲操作的标准中，脉冲速率的偶次谐波周围的相位噪声通过混叠被下变频到基带。后一种机制在文献中被称为迪克效应。本文提出了一种频率控制伺服系统的模型，其输入信号为（已知的）本振相位噪声S/sub /spl phi//（f），输出信号为（未知的）闭环工作时标准相位噪声S/sub /spl phi//（f）。通过迪克效应在稳定的LO上混叠而增加的过量白色频率噪声的水平可以与自由LO相位噪声的特性在分析上相关。由此，然后可以通过基于幂律模型的通常转换公式获得迪克效应的典型稳定性极限（具有斜率/spl τ//sup-1/2/）。
In cold-atom frequency standards based on the Ramsey double interaction method, the phase noise of the interrogating signal appears as a random "end-to-end phase difference", thereby introducing frequency noise in the loop. This phenomenon is analyzed in this paper in the Fourier frequency domain, using phase noise power spectral densities S/sub /spl phi//(f). In continuously operated standards, the excess noise thus introduced is servoed out in the long term to become eventually smaller than the atomic shot noise, whereas in standards with pulsed operation the phase noise around even harmonics of the pulse rate is down-converted by aliasing to base band. This latter mechanism is referred to in the literature as Dick effect. In this paper, a model of the frequency control servo system is proposed, in which the input signal is the (known) local oscillator (LO) phase noise S/sub /spl phi//(f) and the output signal is the (unknown) phase noise S/sub /spl phi//(f) of the standard in closed loop operation. The level of excess white frequency noise added by aliasing on the stabilized LO through the Dick effect can be related analytically to the characteristics of the free LO phase noise. From this, the stability limitation (with slope /spl tau//sup -1/2/) typical of the Dick effect can then be obtained by the usual conversion formulas based on the power law model.