Fuzzy control based frequency synchronization using GPS carrier phase measurements

Frequency synchronization using GPS carrier phase measurements based on fuzzy controller is presented. The frequency offset of the remote OCXO (Oven-Controlled Crystal Oscillator) with respect to the primary atomic clock is precisely estimated in real time by performing the GPS carrier phase single-difference and time-difference. Through the D/A converter, the remote clock is then steered to synchronize with the master clock. The accuracy of the remote clock can be improved from about 5×10^-9 to about 1×10^-13. Moreover, a new methodology of frequency transfer by performing carrier phase single-difference without resolving the carrier phase cycle ambiguity is discussed. The zero-baseline tests with common high-performance cesium clock show that the methodology we proposed has a frequency uncertainty of 5 parts in 10¹⁶ for averaging times of one day