[time-nuts] Common sky pps errors for any GPSDOs?
Magnus Danielson
magnus at rubidium.dyndns.org
Tue Jan 6 03:13:15 UTC 2009
> For the carrier itself absolute phase measurements cant be done.
> Such phase measurements only have meaning when modulation is present.
Alternating modulation frequency may do it for instance. Choosing a set
of modulation frequencies being relative prime to each other alows for
several readings of alternating cycle ambiguity to be resolved using the
Chinese Reminder theorem. Similar set of frequencies can be used, for
instance multiple of 10 alows the phase of the lower frequency to
determine which of the 10 cycles the next frequency is. However, this is
not easilly extendable to carrier frequency cycles, since it would imply
a very wide modulation, so for that a chinese reminder approach is of
interest. A PRN sequence is just a multiple of these frequencies at the
same time. Alternating PRN length could be used for similar purposes of
course. Multiple simultaneous PRN sequences can be added upon each
other. Using multiple carrier frequencies may also be an interesting
option. Consider for instance COFDM which creates a dense set of
carriers using IFFT modulation and FFT demodulation.
Cheers,
Magnus
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