Re: [Discuss-gnuradio] GPS Signals recorded IQ samples file

[Francisco Albani]

Wang: Sounds good! Thanks! Did you try it?

Jean: many many thanks for sharing all the scripts! Your paper has caught my attention. I will print it and read it.

Marcus: I was not expecting to "see" the signal because I already knew it was under noise floor. My conclusion of "signal absence" was after my GPS receiver was not able to decode it when I replayed it with an USRP. However, due to my little knowledge of GPS, it did not occur to me any other way of searching, so I thank you for your suggestion. I nearly killed my pc with a naive approach. :P I need a wiser one.

Sylvain: interesting. I will try that too. Thanks!

2015-08-21 9:07 GMT-03:00 Sylvain Munaut <address@hidden>:

Hi,

> are you sure you did not see GPS? The problem is that GPS is often below the
> thermal noise floor and only detectable by the virtue of processing gain.
> I'd try and take a whole lot of samples (like: 2s worth of samples), and
> calculate the autocorrelation[1]. You should see peaks at multiples of 1 ms,
> because that's the spreading code's period.

You can also square the signal, then decimate it a bit and FFT it and
you'll see peaks at whatever doppler the sat currently has. (so you'll
see different peaks for different sats).


Cheers,

    Sylvain

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