Performance of a PID phase lock loop with Kalman filtered input data [GPS data]

The performance of a rubidium oscillator disciplined to Global Positioning System (GPS) satellite time transmissions is presented together with the phase look loop technique used. The results show an offset frequency accuracy of 1.0×10^-11, while maintaining a phase accuracy of 300 ns versus universal time code (UTC). Typically, the offset frequency error was ⩽2.0×10^-12. Results of analyzing recently acquired GPS data are presented. The fractional frequency stability of least squares estimates performed on the data demonstrate that one can at best expect 2.0×10^-11 frequency accuracy with an OCXO, and can expect accuracies of 2.0×10^-12 (typically) with rubidium oscillators