[time-nuts] Carrier phase tracking

Magnus Danielson cfmd at bredband.net
Mon Feb 19 16:09:39 EST 2007


From: Peter Vince <pvince at theiet.org>
Subject: [time-nuts] Carrier phase tracking
Date: Mon, 19 Feb 2007 16:30:04 +0000
Message-ID: <v04210103c1ff804180ba@[10.0.0.3]>

> I sort of understand the idea of correlation in order to receive the 
> signals from several satellites all on the same frequency, but I 
> wonder if someone has a simple explanation of how the carrier phase 
> can be tracked when there are several carriers all at once?  Does it 
> rely on the different Doppler-shifts making them distinguishable?

No. GPS satellites have unique code sequences which have been chosen to be
orthogonal, such that when one correlates the code of a satellite in one
channel other visible sats will end up as suppressed noise, tracked or not.
Also, in practice will all sats be at different frequencies due to their
orbital positions and your position. They only briefly have the same frequency,
but the code separation ensures that this is not a problem.

Cheers,
Magnus



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