The Research Of High Precision Time Synchronization Method Based On Satellite Timing

The significance of time is self-evident.With the development of science and technology,the precision of time synchronization is becoming more and more important in communication,military and space exploration,and how to achieve high-precision time synchronization have become a hot topic.In this paper,a high precision time synchronization method based on satellite timing is proposed,this method takes into account the all-weather and all-time coverage in the global characteristics of satellite timing signals,and satellite receiver outputs 1PPS signal that has higher long-term average accuracy and long-term stability characteristics,as well as the OCXO short-term high stability characteristics.Using the satellite timing signal to tame the OCXO,the OCXO as a frequency source to output high-precision frequency signal after taming,which can constitute high precision time synchronization system based on satellite timing.In the study of high-precise time synchronization system based on satellite timing,satellite receiver outputs the 1PPS signal after locking the satellite,the signal as a reference frequency signal.The function of frequency multiplication,Frequency division and time interval measurement is implementing in FPGA,first,the process of frequency multiplication and frequency division is performed,then,time interval measurement method using pulse-counting method to measure the time interval bias between the 1PPS signal and the 1Hz signal divided by OCXO,The FPGA generates an interrupt after the measurement is complete.The data processing module reads the time interval bias value from the FPGA,in order to obtain accurate estimation data,the data processing program includes using the sliding median algorithm to remove the outliers in the data sequence,and using unbiased FIR filtering algorithm to filter the time interval bias to eliminate the burr and weaken the random jitter,the control quantity calculated by using digital PID control algorithm.The High-performance D/A conversion module converts control quantity to analog voltage to input the OCXO,adjusting OCXO output stability,and ultimately 1PPS signal and the OCXO frequency signal maintain a high degree of synchronization,the error within 30 ns.The satellite signal is susceptible to interference or loss,and can't be used as a reference frequency signal,this paper discusses how to use the predictive control algorithm to adjust the crystal by the historical data so as to keep the output frequency high precision for a period of time.Based on the above-mentioned technology,this paper designs a prototype of time synchronization system based on satellite timing,introduces the systematical hardware design,software design flow,the filter algorithm and control algorithm.The upper computer software is designed to test the system,by analyzing the experimental data,this method can improve the OCXO long-term average accuracy and long-term stability to a certain extent,as the frequent source of high precision time synchronization system.