An atomic clock steering algorithm is proposed by utilizing a DPLL equivalent to a Kalman filter with a delay.The close-loop system transfer function and the close-loop error transfer function are derived.The implement structure of the DPLL

and the adjustment to the atomic clock to be steered in each time are shown.A method for choosing the parameter such that the output frequency stability is optimal is also carried out.Then

a twice steering algorithm by means of two same DPLLs in the cascade form is proposed.The theoretical analyses and simulations all indicate that it is easier to choose parameters in the algorithm than the traditional algorithms

the output synchronizes to the first input and its frequency stability is optimal.The twice steering algorithm is useful for designing the phase-locked oscillator

where the number-controlled oscillator is first steered to a hydrogen maser and then steered to a cesium clock.The algorithm is also useful for forming a GNSS time.The method first steers BDT to UTC(BSNC)

and then steers BDT(MC) to the steered BDT.