Abstract:
Objectives Real time precise point positioning(RT-PPP) technology can realize one-way timing with sub-nanosecond precision and daily stability of 1×10－14 level. Clock steering affects the stability of the receiver's output time-frequency signal, however, inappropriate clock steering parameters can degrade the short-term stability of the receiver's oscillator.
Methods To combine the short-term stability of the oscillator and the long-term stability of the RT-PPP, we propose a phase-locked loop clock steering model for the RT-PPP time-frequency receiver. The noises of the system are analyzed. And the parameter design method of the second-order phase-locked loop is proposed. Experiments were carried out with the clock steering model and designed parameters used in the RT-PPP time-frequency receiver.
Results Experimental results show that the frequency stability of the RT-PPP time-frequency receiver is 4.344 4×10－12 at 1 s, 1.102 9×10－14 at 1 d, the frequency stability of the time intervals shorter than 300 s can get close to the free-running Rubidium clock, the frequency stability of the time intervals longer than 300 s can get close to the RT-PPP.
Conclusions The proposed clock steering model and parameter design method can well realize the combination of the oscillator's short-term stability and the RT-PPP's long-term stability.
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