Research On Multi-channel Frequency Phase Comparison Method Based On Event Timing

With the rapid development of time-frequency measurement and control technology,as well as the accuracy required in the people’s livelihood and national defense,the performance of time and frequency sources gradually becomes crucial.Since the accuracy of the time and frequency source reaches the order of E-18,the accuracy of the time-frequency measurement instrument limits the role of the time-frequency source in various application fields.Therefore,the demand for high-precision and low-noise time-frequency measurement system becomes increasingly urgent.At present,various scientific research institutions and professional companies all over the world are committed to the research and development of precision time-frequency measuring equipment and related products,which have achieved a desirable performance.Related research results include PCO(2.5E-14/s)produced by Timetech in Germany,A7(5E-14/s)produced by Quartzlock in the UK,and TSC MMS(2.5E-13/s)produced by Microsemi.The above mentioned products are all multi-channel phase comparison instruments that adopt the principle of time interval counting,which are commonly used in domestic.The JPL laboratory of NASA in the United States has developed a multi-channel frequency standard stability analyzer FSSA,which utilizes event timer ET instead of time interval counting unit TIU,thus achieving the highest accuracy performance at the time(the Allan variance of 2E-15/s);On the other hand,domestic products are still in the catch-up stage.The domestic equipment,such as the self-designed multi-channel phase comparators(2E-13/s)invented by the National Institute of Metrology and Suin Digital Instruments cooperation,mostly adopt the DMTD method based on the principle of time interval counting.At present,there is no domestic high-precision multi-channel phase comparator with ET,therefore,it is necessary to solve the problem of independent property rights in this aspect.Due to technical blockage,production stoppage and other problems,even if foreign countries have reached a very high level of performance,China is always lack of domestic high-precision measuring equipment,so it is necessary to solve the problem of the independent property rights of the high-precision phase comparator based on ET;Besides,in the practical application of time and frequency,a single frequency source is prone to drift,so it requires multiple atomic clocks to select a reliable time and frequency source to output through seamless switching.Therefore,it is also necessary to study the method of multichannel frequency phase comparison.First,this thesis analyzes the shortcomings of TIC method for multi-channel measurement in previous experiments.Then it designs the event timer used in this multi-channel frequency phase comparison method.The multi-channel frequency phase comparison method realized by the event timer is then introduced.Meanwhile,the upper machine is designed by LabVIEW,which adopts the concept of modular design and decouples individual modules.As a result,it shows strong expandability that increases the reusability of the program and the convenience of subsequent modification.The proposed multi-channel frequency phase comparison method can simultaneously measure and monitor the relative stability of any independent frequency source and one source at any frequency.In addition,any two sources connected to the system can be compared in pairs at any time without hardware reconfiguration.The measured standard deviation is better than 1.5E-14 s,which fundamentally solves the dead zone problem.What is more,the multi-channel arbitrary phase comparison and continuous measurement without fixed reference channel and kilohertz test speed is realized,which solves the problem of independent property right of high-precision multi-channel phase comparator with ET method.