The Research On Transient Frequency Stability Of Frequency Source With Time

The frequency source performance is getting higher and higher in the satellite navigation,instrument,communication and other industries.Frequency stability is an important index of frequency source performance.Stability includes transient stability,short-term stability,and long-term stability.Transient stability plays an important role in the research of remote noise and short-term stability of phase noise.Due to the complexity of analog circuits and the limitations of measuring gates,traditional measurement methods cannot measure transient stability.With the development of digital technology,the measurement of transient stability has been resolved.In the traditional frequency source stability measurement,there is usually a frequency source with higher accuracy as the frequency standard,but with the significant increase in frequency source technical indicators,it is often difficult to find a standard device that meets the requirements.Based on a large amount of research work by us and our predecessors,we found that in the absence of an external reference standard,the frequency source can be stable to its own frequency due to the difference between the value of the noise kept at different times and the existing value.The indicators are precisely measured,combined with analysis of the frequency-domain delay line/mixer-type discriminators.This paper proposes a new method for measuring the transient stability of a frequency source by using the frequency source delay(phase shift),that is,by delaying(phase-shifting)the signal of the frequency source and comparing the signal with its own signal to obtain the measurement of transient stability.In this measurement scheme,the measured signal after the delay is used as the clock signal of the A/D converter,and the measured signal without delay is collected.The obtained digital value is the phase difference before and after the delay of the measured siginal,so that we can calculate the transient stability.This article introduced the principle of the measurement scheme in detail and designed a specific measurement scheme,introduced the hardware and software design,and measured the transient stability of commercial voltage controlled crystal oscillator and passive cesium clock.The experimental results show that the transient stability can be measured at the magnitude of 10E-5 in transient hundred nanosecond.The crystal oscillator is the most widely used frequency standard and it is of great significance to the performance improvement of the crystal oscillator.Based on the analysis of the change of frequency source stability curve and the corresponding noise situation,a method of improving the stability of crystal oscillator by using the characteristics of high delay and stability is proposed by using the rule of crystal oscillator stability 1? curve before the second.This paper introduces the principle of digital edge effect and stability improvement,and designs an experimental scheme.The experimental verification improves the transient stability and short-term stability of the crystal oscillator by more than two times.This article designs the experimental scheme of digitized frequency originating from the standard transient stability measurement and the experimental scheme to improve the stability of the crystal oscillator.It is of great significance for the understanding of the frequency source and the improvement work.