铷原子频标的时频处理技术研究

发布时间：2018-05-04 08:03

本文选题：频率链接 + 频率稳定度　；参考：《西安电子科技大学》2014年硕士论文

【摘要】：原子钟利用原子的超精细能级间跃迁所辐射的频率对时间进行度量。由于它计时的准确性和稳定性,原子钟在过去的五十年中已成为航空航天、导航定位、通信以及科学测量等领域中不可或缺的器件之一。原子钟主要包括物理部分和线路部分,是高稳定度晶体振荡器的物理锁定系统,其性能主要取决于物理部分和线路部分的配合。通常情况下,物理部分由于受到外界温度变化和自身老化等因素的影响而不能达到理想的效果,同时由于线路部分需要通过多级倍频、混频、合成等复杂频率变换,将物理部分跃迁频率锁定到高稳定度晶体振荡器上,在这个过程中,会引入附加噪声,影响了原子钟的短期稳定度指标。针对物理部分和线路部分的不足,可以分别利用线路部分的补偿以及精密频率链接等时频信号处理技术来解决。本文基于广泛使用的铷原子钟,针对以上情况完成了以下几个方面的工作：1.针对铷原子钟温度漂移问题进行了温度补偿技术研究。本文利用原子钟的输出随温度变化的重现性的稳定性,采用直接数字频率合成器对铷钟进行补偿,在没有对被补偿频率源的自身短期稳定度产生太大影响的前提下,减小了铷原子钟的温度系数。验证了该设计方法的可行性和有效性。2.针对铷原子钟长期漂移造成频率准确度降低的问题进行了研究。本文利用GPS接收机输出的1PPS信号的长期平均无漂移的的特性,设计了基于GPS的1PPS的铷原子钟驯服系统。对比驯服前后的实验结果,发现输出频率的准确度得到了提高。3.针对传统铷原子钟进行了线路简化研究。在研究传统线路的基础上,根据周期性信号间相位比对过程中的相位群规律性变化,提出了对线路链接部分的简化处理技术,即将一个特殊频率值为13.669375MHz的VCOCXO,经过500倍频后可直接得到铷原子能级跃迁的激励信号,再经过钟伺服对VCOCXO进行锁定,从而改善了13.669375MHz VCOCXO的输出频率信号指标。但13.669375MHz的信号往往不能直接被使用,可进一步通过基于周期性信号间的精密频率链接技术,将拥有铷原子能级跃迁指标的13.669375MHz VCOCXO信号的高准确度传递给10MHz VCOCXO的标准频率输出。经改进后,相噪指标得到了有效改善。
[Abstract]:Atomic clocks measure time using the frequency of transitions between the hyperfine energy levels of an atom. Due to the accuracy and stability of its timing, atomic clock has become one of the indispensable devices in the fields of aerospace, navigation and positioning, communication and scientific measurement in the past 50 years. Atomic clock mainly includes physical part and circuit part. It is a physical locking system of high stability crystal oscillator. Its performance depends on the cooperation of physical part and circuit part. In general, the physical part can not achieve the ideal effect because of the influence of the external temperature change and the aging of itself, and the circuit part needs the complex frequency conversion, such as multistage frequency doubling, mixing, synthesizing and so on. When the physical partial transition frequency is locked on the high stability crystal oscillator, additional noise will be introduced in the process, which will affect the short-term stability index of atomic clock. Aiming at the deficiency of the physical part and the line part, the time-frequency signal processing technology, such as the compensation of the circuit part and the precise frequency link, can be used to solve the problem. In this paper, based on the widely used rubidium atomic clock, we have done the following work: 1. The temperature compensation technique for the temperature drift of rubidium atomic clock is studied. In this paper, using the stability of the reproducibility of atomic clock output with temperature variation, the direct digital frequency synthesizer is used to compensate the rubidium clock without too much influence on the short-term stability of the compensated frequency source. The temperature coefficient of rubidium atomic clock is reduced. The feasibility and effectiveness of the design method are verified. The reduction of frequency accuracy caused by long-term drift of rubidium atomic clock is studied. In this paper, a rubidium atomic clock taming system based on GPS and 1PPS is designed based on the long-term average no drift characteristic of 1PPS signal output by GPS receiver. By comparing the experimental results before and after acclimation, it is found that the accuracy of output frequency is improved by .3. The circuit simplification of rubidium atomic clock is studied. On the basis of studying the traditional circuit, according to the regular change of phase group in the process of phase comparison between periodic signals, the simplified processing technology for link part of the line is put forward. VCOCXO, which has a special frequency value of 13.669375MHz, can directly obtain the excitation signal of rubidium atomic energy level transition after 500 times frequency, and then lock the VCOCXO through clock servo, thus improving the output frequency signal index of 13.669375MHz VCOCXO. However, the signal of 13.669375MHz can not be used directly, and the high accuracy of 13.669375MHz VCOCXO signal with rubidium atomic level transition index can be transferred to the standard frequency output of 10MHz VCOCXO by means of precise frequency link technology based on periodic signal. After improvement, the phase noise index is improved effectively.
【学位授予单位】：西安电子科技大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM935.115

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