RE: [Discuss-gnuradio] DBSRX used for GPS: cycle slip

[Heckler, Gregory W. (GSFC-596.0)]

Have you ruled out the USRP overflowing? I have had that problem bite me too. It causes all of the tracking
channels to dump in my receiver, but I could see how it could also cause a jump in the frequency estimate
(delay in time domain == shift in frequency domain) coming out of your FFT acquisition.

-----Original Message-----
From: address@hidden on behalf of Chris Stankevitz
Sent: Mon 6/2/2008 8:54 PM
To: Heckler, Gregory W. (GSFC-596.0)
Cc: address@hidden
Subject: Re: [Discuss-gnuradio] DBSRX used for GPS: cycle slip

Heckler, Gregory W. (GSFC-596.0) wrote:
> I was referring to the Doppler estimate output by your PLL over time
> (traditional tracking), whereas
> you indicated that you were looking at repeated acquisition attempts.

Greg,

While performing traditional tracking with a PLL using "prompt"
accumulations, I noticed my PLL could not keep track.  As a debugging
tool I conducted repeated acquisitions and it was there I noticed that
the freq was suddently changing -- aha the source of my PLL problem!

This image should give you an idea of what we are doing.  It's a matlab
plot of various outputs from our traditional tracker.

http://img233.imageshack.us/img233/4064/gpswm9.gif

Thanks, I will take a look at the frequency being passed to DBSRX.

Chris


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