时间频率学报

针对目前电话授时系统中授时准确度低的缺点,提出了一种基于PN码的时延测量方法,该方法将PN码引入电话信道的时延测量中,服务器端将PN码信号经幅度调制和DA转换后通过电话信道传输至用户端,用户端先对输入信号进行AD采样,幅度解调,再利用PN码信号的自相关特性对其进行快速捕获,进而完成信道时延测量。通过实验测试表明:该方法可以用于电话信道的时延测量,能够将不同电话端局间的时延测量波动值由毫秒级减小到125μs,从而为提高电话授时准确度打下了基础。

A new time delay measurement method is proposed to improve the timing accuracy in telephone time service system, PN code is used to measure time delay in the method. The PN code is modulated firstly by sine wave, and then the modulated signal is converted to analog signal. The analog signal is transmitted from time server to user terminal through telephone channel. Then the received analog signal is converted to digital signal which is demodulated to PN code signal. Because PN code can be quickly captured duo to its auto-correlation characteristic, it can be used to measure the time delay in telephone channel. The experiment results between different telephone interoffice proved that the time delay fluctuation in telephone channel can be decreased from millisecond to less than 125 microseconds, it is a foundation work for improving the accuracy of telephone time service.