High Stability Crystal Oscillator Based On Atomic Resonator

As a time-frequency reference,the frequency source has a wide range of applications in fields of timing,positioning,navigation,communication,and aviation.Frequency stability is one of the important indicators of the frequency source,and its directly reflects the performance of the frequency source.With the development of science and technology,the requirements for frequency stability indicators are getting higher and higher in various occasions.Therefore,it is of great significance to study the frequency stability in depth.In this paper,we test frequency stability curve s of a large number of crystal oscillators and find that there are “inflection points” in curves of all crystal oscillators.Before the “inflection point”,the frequency stability of the crystal oscillators increase gradually with increase of sampling time.After the “inflection point”,the opposite is true.However,due to the internal structure of the crystal oscillator and the processing technology,there are differences in the position of the "inflection point" of the frequency stability curve of the crystal oscillator produced by different manufacturers and the number of "inflection points".The atomic frequency standard is based on the crystal oscillator.The atomic resonator is used to lock the output frequency of the crystal oscillator.After the curve is “inflection point”,the frequency stability can still be improved,so the crystal oscillator after the frequency is locked is best frequency stability.At present,many scholars at home and abroad focus on improving the stability of the atomic frequency standard frequency on the improvement of its physical part(atomic resonator),in addition to the physical part,the frequency variation characteristics of the internal crystal oscillator itself also have a great influence on the frequency-locking effect.In this paper,the Rubidium atomic resonator is used.Through theoretical analysis and experimental verification,it is found that the crystal frequency locking with different characteristics will have different effects.Then,by using a Rubidium atomic resonator to lock a large number of crystal oscillators,the change of the frequency stabilit y curve of the crystal oscillator before and after the frequency lock is tested and observed.Comparing the test results of these crystal oscillators,it is found that the "inflection point" of the frequency stability curve is located.When the time is close to the modulation period of the atomic resonator,the crystal oscillator has a better freque ncy-locking effect.Then,by the design scheme,a closed frequency-locked loop is realized to lock the output signal of the crystal oscillator that meets the abo ve characteristics.Comparing the original atomic frequency standard and the crystal frequency stability curve after frequency-locking,the overall curve of the latter is located below the former,and the frequency stability of the latter in the different sampling time intervals is at least 2 times higher than the former.