A composite clock for robust time–frequency signal generation system onboard a navigation satellite

This research designs a robust time–frequency signal generation system based on the composite atomic clock onboard a navigation satellite, which focuses on the atomic timescale (ATS) generation algorithm and the paper time steering technology of physical realization signal. Combined with the improved ATS algorithm of weighted Kalman, we use the precise clock error data of Center for Orbit Determination in Europe to calculate the single-satellite paper time with higher stability than the classical ALGOS algorithm as a reliable steering reference. The cost function combined with genetic algorithm is designed, and a strategy for optimizing the parameters of the Kalman equivalent digital phase-locked loop control system through adaptive iterative optimization is proposed to obtain the optimal steering value with greatly improved precision. Simulations show that with the improved composite paper time obtained by the single-satellite atomic clock group set as the reference, the time steering error of the steered signal can be maintained within ± 0.09 ns, and the long-term stability is 4.84E−15/1 day. Compared to the single master-clock and ALGOS scheme, respectively, the time steering error is reduced by 58% and 26%, and the frequency stability at 10,000 s is improved by 47% and 15%. Study results provide scheme support for frequency stability performance improvement and reliable application of single-satellite autonomous timekeeping.