[time-nuts] Compensating phase differnces in dual frequency GPS receviers?

Attila Kinali attila at kinali.ch
Thu Dec 1 08:37:52 EST 2011


On Wed, 30 Nov 2011 19:56:25 -0800
Peter Monta <pmonta at gmail.com> wrote:

> Hi Attila,
> 
> > [ L1 / L2 timing differences ]
> > How do dual frequency receivers deal with that?
> 
> I've also been toying with the idea of an inexpensive dual- or
> tri-band GPS SDR, especially since there are now quite a few
> satellites emitting L2C, the civil L2 signal.  (Though I'd still like
> to try my hand at the fancy L2 semicodeless schemes.)
> 
> I think that manufacturers calibrate out the timing differences
> between channels (as well as group-delay variations within a channel).
>  There must be some remaining error, though, e.g. over temperature,
> depending on the filter technology.

So, that'd mean there would be an automatic calibration system inside
the device, because i dont have any equipment with which i could
calibrate delays over a temperature range.

 
> ObTimeNuts:  There's an interesting recent thesis on GPS for time and
> frequency metrology:
> 
> http://www.ptb.de/cms/fileadmin/internet/fachabteilungen/abteilung_4/4.4_zeit_und_frequenz/pdf/Feldmann_2011_Dissertation.pdf
> 
> Section 5.1.3 has a few words on exactly this channel-filter-delay
> issue.  The author measures a coefficient of 20 ps per degree for a
> pair of receivers.

Nice disertation, but i cannot see how you come to the conclusion
that this temperature coefficient is from the input RF chain.
The measurement shows only a general time shift of the whole device.
And the author does not draw any conclusion from it.

			Attila Kinali

-- 
Why does it take years to find the answers to
the questions one should have asked long ago?




More information about the time-nuts mailing list