[OpenSource_GPS] a question about pull_in function in the open code

[tongtong wang]

Hi

Many thanks for your reply.
Is there any publication about this method of coherently integrating
the dither and prompt correlators?
Want to know more about why it can get a higher SNR in this way...
Sorry for the bothering.

Best regards,
Tongtong

On 5/22/07, Clifford Kelley <cwkelley at earthlink.net> wrote:
> Tongtong,
>
> In this part of the code we are trying to create a "pseudo" prompt correlator by coherently
> integrating the dither and prompt correlators which are actually being used as "early" and "late"
> correlators with 1/2 chip spacing.  This creates a higher signal to noise than a non-coherent integration.
>
> I hope this answers your question.
>
> Best regards,
>
> Cliff
>
> -----Original Message-----
> >From: tongtong wang <tongtongwang at gmail.com>
> >Sent: May 21, 2007 10:53 AM
> >To: opensource_gps at lists.psas.pdx.edu
> >Subject: [OpenSource_GPS] a question about pull_in function in the open code
> >
> >hi, there
> >
> >Many thanks for your sharing the GPS code.
> >
> >I got a question about the tracking lock loop function in the
> >CH_PULL_IN procedure.
> >
> >"  q_sum = c->accum.q_dith + c->accum.q_prompt;
> >  i_sum = c->accum.i_dith + c->accum.i_prompt;
> >  if (i_sum != 0 || q_sum != 0)
> >    theta = fix_atan2 (q_sum, -i_sum); "
> >
> >Is fix_atan2 (q_sum, -i_sum) the phase detecter?
> >Why you use Q=q_sum & I=-i_sum instead of rss(c->accum.q_dith ,
> >c->accum.q_prompt) & rss(c->accum.i_dith ,  c->accum.i_prompt) in the
> >atan2 part?
> >
> >Hope I can get answer here.
> >Thanks again.
> >
> >//tongtong
> >
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>