Use of GPS carrier phase for high precision frequency (time) comparison
Quality in time metrology depends on the performance of the atomic clocks and the means for time-frequency comparison. New generation of caesium standards have accuracy below 2x10-15 and the classical common-view method is no longer satisfactory. Use of GPS carrier phase combined with code measurements is a promising technique for the accurate comparison of remote clocks. This paper discusses some error sources disturbing the uncertainty of the comparison using the code-phase method, mainly on the equipment capability and the data processing strategy. In fact, the receiver system, comprised with the main unit, the antenna and cables, is very sensitive to the environmental temperature and this may seriously influence the comparison result. Due to problems with the raw data or some defeats in the data processing, there often exist phase discontinuities in comparison results, ranging from several hundred ps up to several ns, which may be mistaken as drifts produced by the compared clocks and increase the uncertainty of the carrier-phase method so as to limit its application for highly accurate frequency transfer. A number of equipment setting up conditions and a multi-day data processing strategy are proposed in which the temperature effect and the discontinuities are significantly reduced and the frequency stability is improved. An uncertainty of 1X10-15 for an averaging time of 1 day is expected.
KeywordsAtomic clock time and frequency comparison GPS carrier phase frequency stability
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- Allan D., Weiss M. (1980). Accurate time and frequency transfer during common-view of a GPS satellite. In: Proc. IEEE Freq. Contr. Symp., Philadelphia, USA, pp 334–356.Google Scholar
- Baeriswyl P., Schildknecht T., Utzinger J., Beulter G. (1995). Frequency and time transfer with geodetic GPS receivers: first result. In: Proc. 9 th EFTF pp.46–51.Google Scholar
- Douglas R.J., Popelar J. (1994). PTTI applications at the limit of GPS, Proc. 26 th PTTl, pp 141–152.Google Scholar
- Dudle G., Overney F., Prost L., Schildknecht T., Springer T. (1999). Transatlantic time and frequency transfer by GPS carrier phase. In: Proc. EFTF, IEEE IFC Symposium. Google Scholar
- Dunn C., Jefferson D., Lichten S., Thomas J.B., Vigue Y. (1993). Time and positioning accuracy using codeless GPS. In: Proc 25th Precise Time and Time Interval Application Planning Mtg., Marina Del Rey, Ca, pp 169–182.Google Scholar
- Jiang Z., Petit G. (1999). Accurate frequency comparison using GPS carrier phase, submitted to Special Issue of the IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control on Frequency Control and Precision TimingGoogle Scholar
- Larson K.M. (1998). Time transfer using the phase of the GPS carrier. In: Proc. IEEE FCS, pp 292–297.Google Scholar
- Petit G., Thomas C. (1996). GPS frequency transfer using carrier phase measurements. In: Proc. 50 thIEEE FCSpp 1151–1158.Google Scholar
- Petit G., Thomas C., Jiang Z., Uhrich P., Taris F. (1998). Use of GPS Ashtech Z12T receivers for accurate time and frequency comparison. In: Proc. IEEE FCS pp306–314Google Scholar
- Petit G., Jiang Z., Taris F., Uhrich P., Barillet R., Hamouda F. (1999). Processing strategies for accurate frequency comparison using GPS carrier phase. In: Proc. EFTF, IEEE IFC SymposiumGoogle Scholar
- Rothacher M., L. Mervart (1996). Bernese GPS software version 4.0 (Published by Astronomical Institute University of Bern)Google Scholar