Re: a question about pull_in function in the open code

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 <[email protected]> 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 <[email protected]>
> >Sent: May 21, 2007 10:53 AM
> >To: [email protected]
> >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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>