Study Of Time Discipline Technology Based On Dual One-Way Ranging

With the development of science and technology, time-frequency with a higher accuracy is required. Due to their low costs and their advanced frequency resolution, disciplined quartz oscillators with high-precision has been widely used. Nevertheless, existing disciplined frequency products cannot be used directly to some specific areas. A method of GPS disciplined oscillators combine with Dual One-Way Ranging(DOWR) is thus presented in this paper, which integrated time-synchronization with inter-satellite ranging for the formation satellites in a project.This paper firstly analyze the frequency stability of quartz oscillators mathematically, based on which a design of time synchronization for the whole formation satellites system is proposed. The whole system consists of a master with a OCXO and a slave with a TCXO. The OCXO is disciplined with respect to GPS while the TCXO is disciplined with respect to OCXO. The phase difference between the pulse of GPS and of OCXO is measured in FPGA via a kind of high-precision timeinterval measurement technique, which is implemented by a coarse counter combined with a carry chain. In order to eliminate the random jitter of GPS pulse, a Kalman filter is used to process the difference data. The phase difference is then converted into the control voltage of the quartz oscillators by PI controllers. The TCXO in the slave is disciplined in the same way as OCXO despite the phase difference between them is measured via DOWR.The optimized loop gain parameters are obtained by analyzing the simulation model of the whole disciplined system. Finally, a prototype is implemented, and by testing performance of which it is concluded that the disciplined quartz oscillators maintain their short-term frequency stability, while the long-term frequency stability of them is significantly improved.