According to the features of filtering algorithm used in GPS

an improved disciplined method using Global Positioning System one pulse pre-second (GPS1PPS) timing signal is proposed in this paper.This unbiased moving average filtering algorithm can eliminate sawtooth errors of GPS1PPS signal and produce an unbiased evaluation of local clock state by using linear regression estimate.Digital Phase-Locked Loop (DPLL) is used to make GPS1PPS timing signal tracked steady by local clock and combine the short term stability of crystal oscillator and long term stability of GPS1PPS timing signal

which ensure high frequency stability and accuracy of local frequency standard when GPS timing signal is lost.The results of MATLAB simulation and real measurement have proved that this method can improve long stability and accuracy of frequency

and Allan variance of frequency stability of crystal oscillator OXCO-131 pre-day in a real system has been improved 3 orders of magnitudes and reached 3.5E-12.