Development Of The Frequency Standard Redundant Switching And Multimode Distribution System

Frequency standard is a kind of equipment which can generate standard frequency signal with high accuracy and stability,and it is widely used in daily life and scientific research.The stable and continuous operation of frequency standard ensures the normal operation of daily systems including power grid system,mobile communication,Internet,global positioning system,etc.With the continuous progress of manufacturing technology and technical level,the reliability of frequency standard is higher and higher.However,the working environment of the frequency standard is complex.In the long-term work,the electromagnetic interference,temperature change,vibration interference and component aging of the surrounding environment may affect the working state of the frequency standard,resulting in abnormal output of the frequency standard,thus affecting the performance of the overall system.In this case,redundant configuration of frequency standard can effectively improve the reliability and stability of the system.In case of failure or damage of the main frequency standard,the frequency standard with redundant configuration can be used as a backup to timely provide frequency signal for the main frequency standard time-frequency system to ensure the normal operation of the system.With the rapid development of time-frequency technology,more and more time-frequency systems have developed into multi-user systems,that is,multiple devices in a system need to be provided with frequency signals by frequency standards.The high-precision frequency standard is expensive and has poor load capacity.It is difficult for a single frequency standard to provide frequency standard signal for a multi-user system.A frequency standard can only provide a reference frequency for a device or system,so the use cost is too high.In addition,the normal frequency standard is limited by its own signal output characteristics and coaxial cable transmission characteristics,and its output mode and transmission distance are limited.Based on the above considerations,this paper studies the method of redundant switching and multimode distribution of frequency standard,and develops the corresponding system principle prototype.When the output of the primary frequency standard fails,the system can detect and quickly switch to the standby frequency standard signal,which improves the stability and reliability of the frequency standard.At the same time,the system has four channels of RF signal output and one channel of optical signal output,which can provide reference frequency for multiple devices or systems,as well as remote devices,enriching the distribution form of frequency standard.The main work of this paper is as follows:(1)Aiming at the output fault of frequency scale,a method of frequency signal detection and fast switching based on amplitude comparison is proposed.Based on the traditional pin RF switch,a new series parallel pin RF switch is designed by adding a shunt device and a matching network on the basis of the traditional pin series parallel switch,which improves the switching speed of the main and standby frequency standards and the isolation between the frequency standards.(2)In view of the poor load capability of the frequency standard band,a robust distributed amplifier circuit is designed.The buffer circuit with dynamic input characteristics is introduced into the distribution amplifier,which greatly improves the anti-interference ability of the system,increases the load capacity of the frequency standard,and enables the frequency standard to drive more devices.(3)According to the characteristics of frequency standard signal and the transmission characteristics of coaxial cable,an optical fiber distribution system of frequency standard signal is designed.In theory,the system can transmit the frequency standard signal for 2.5km.The experimental results show that the proposed redundant switching and multimode distribution system can improve the reliability of the frequency standard,the ability of driving and the ability of remote transmission of frequency signals.The switching speed of frequency standard is 352.60 ns,the isolation between the main and standby frequency standards is 76.33 db,the signal stability is 1.52E-12,and the accuracy is4.29E-12.