On 1/16/11 12:12 PM, Brooke Clarke wrote:
Hi Pete:
The SiGe receiver IC is not much use by itself since you need to
literally be a rocket scientist in order to process its output data.
The GPS1A, with open source software is interesting, but again you need
to be a rocket scientist to modify the code.
Not necessarily...
There are a fair number of 1 bit sampler example codes for GPS receivers
out there.
There's sort of two parts to the problem.. the first one is acquiring
and tracking the PN codes and recovering the NAV message. That's fairly
straightforward.
You can do a FFT type cross correlation, for instance, or just a simple
standard PN correlator. The trick is that you have to allow for the
doppler (that is, it's not just acquiring code phase.. you also need to
get the doppler/clock offset). I'm sure there's sample code out there
(perhaps in the textbook referenced in the first link?)
The next part is actually getting a NAV solution from the raw observables.
That's a bit trickier, but, really, if you're not "computational
performance limited" (e.g. you're not trying for nanojoules/fix on a
cellphone, and can burn a bunch of performance from your PC), the
equations and Kalman filter are doable in Matlab/Octave pretty easily
(and published).
After all, your filter update rate is probably something like 10 Hz or
1 Hz.
BTW, it is possible to get all your observables with 1 second's worth of
data samples. You might even be able to get a nav solution, with some
side information (e.g. ephemeris data... at the 50bps, you're not going
to get the whole almanac in 1 second)
_______________________________________________
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
