Translated Abstract
As the technology becomes more and more advanced, the requirement of time accuracy becomes higher and higher. Time synchronization system is increasingly used in many advanced areas such as national high-tech defense, power system synchronization, deep space exploration and so on. It is becoming more and more important to research and develop a high-precision time synchronization system.
In this paper, we designed a time synchronization system with GPS as the timing source and constant temperature crystal oscillator (OXCO) as the local clock. With the GPS timing, the system controls the frequency of the OXCO, and then output the synchronous signal for other systems. The main work of this paper includes the following three parts.
Firstly, we describe the design of time synchronization system. Calculate the time interval between GPS and the OXCO through the time interval measurement module, and get the time difference of the OXCO. Then eliminate the noise of the clock with the filtering algorithm, and calculate the control amount with the control algorithm. Finally, convert the control amount into the analog voltage signal to correct the output frequency of the OXCO, so as to achieve the purpose of control the accuracy of the time synchronization.
Secondly, in the hardware platform design, we choose the hardware platform based on ARM and FPGA. In the measurement of the time interval, we use the FPGA to measure the rough count value and use the TDC-GP2 module to measure the exact count value. Through this method, we improved the measurement accuracy of the time interval.
Finally, we designed a filtering algorithm based on the median filter and unbiased FIR filter. After remove the outliers from the data we can obtain the more accurate data of the clock error and speed. In the choice of control algorithms, we researched the predictive control algorithm, which improved the synchronization accuracy and synchronization stability of the time synchronization system.
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