基于GPS秒脉冲的参考源实时校正算法

Real-time correction algorithm for reference source based on pulse per second signal of GPS

全球定位系统(GPS)接收机的秒脉冲(PPS)随机误差大,并且板载时钟存在累积误差。在分析GPS秒脉冲的正态分布特性基础上分别提出了秒脉冲参考源和时钟参考源的实时校正算法,其中秒脉冲参考源校正算法对高频脉冲连续累加求平均获取了一秒内脉冲数平均值,以预测秒脉冲与协调世界时(UTC)秒脉冲的时间误差均值作为补偿,生成校正秒脉冲;在均值法求温补晶振(TCXO)实际频率基础上,研究了用于校正时钟参考源的脉冲补偿算法。仿真实验结果表明,采用GPS秒脉冲参考源校正算法后秒脉冲随机误差减小7.5倍;采用时钟参考源实时校正算法校正后产生的12.5 MHz参考源连续9.5 h测试误差低于140 ns。基于GPS秒脉冲的参考源实时校正算法可有效减小误差。

The Pulse Per Second（PPS） signal of Global Positioning System（GPS） receiver has large random error and the onboard clock exists cumulative error. Based on analyzing normal distribution characteristics of the PPS signal of GPS, the real-time correction algorithms for reference source of PPS and clock were proposed. In the real-time correction algorithms for reference source of PPS, the average value of pulse number in one second was obtained by averaging high frequency pulse accumulation, the average value of time error was obtained by averaging the pulse number of the time error between predict second pulse and coordinated universal time（UTC）, thereby generating corrected second pulse. On the basis of the actual frequency of Temperature Compensated Crastal Oscillato（TCXO） which is obtained by the average method, pulse compensation algorithm was studied which is used for correcting the clock reference source. Simulation and experiment results show that the random error decreases 7.5 times by the use of real-time correction algorithm for reference source of PPS. Test error is less than 140 ns in 9.5hours by the use of real-time correction algorithm for reference source of clock. The real-time correction algorithm for reference source can effectively reduce the errors based on PPS signal of GPS.