| 主权项 |
1. A method for instantaneous and continuous determination of a relative time offset between non-collocated frequency sources having a relative frequency drift therebetween, said determination being carried out at a required nanosecond level accuracy, the method comprising:
providing at least two non-collocated timing units located at known positions, each timing unit comprising a frequency source and a collocated receiver, wherein each said receiver is synchronized by a synchronization signal supplied by said frequency source and is operative to receive an external signal stream defining a time-line and to derive therefrom a stream of pseudo-range sample and integrated Doppler sample pairs, to generate, for each individual pair in at least a subset of said pairs, a periodic pulse synchronized with said frequency source, thereby to define a periodic pulse corresponding to said individual pair and to output each individual pair in said subset, simultaneously with the individual pair's corresponding periodic pulse; disciplining of frequency drift between the frequency sources at a frequency domain including computing, and applying to the frequency sources, corrections of a relative frequency drift between each frequency source and a single time source, said disciplining being limited by the following condition: the product of a duration of any time period extending between adjacent discrete points of time in a sequence of discrete points of time, times the sum of all frequency corrections effected during said time period divided by a frequency value characterizing the frequency sources, is at least one order of magnitude less than the required accuracy; and determining time offset between said non-collocated frequency sources at each discrete point of time in said sequence of discrete points of time. |
