Re: Galileo Frequency Shifting and Filtering

Glad to see you got it working – I got confused by the frequencies from
the first spectral diagram you shared, about which Daniel correctly
noticed it was slightly wrong. My bad!

Best regards,
Marcus

On 2/28/23 18:33, David Dima wrote:
> Here is the proof:
> imagen.png
> Many many thanks to everyone!
> David
>
> El mar, 28 feb 2023 a las 18:27, David Dima (<daviddimavd@gmail.com>)
> escribió:
>
> All right guys, I got it, it works now. The central frequency
> should have been 1911.795 MHz instead of 1189.5MHz. The final
> configuration results as follows:
> imagen.png
>
> imagen.png
>
> Thank you very much to everybody!
> Best regards,
> David
>
> El mar, 28 feb 2023 a las 18:17, Marcus Müller
> (<mmueller@gnuradio.org>) escribió:
>
> Hi David,
>
> please stay in the habit of keeping the mailing list in CC!
>
> Can you please write this email to the mailing list?
>
> Thanks,
> Marcus
>
> On 28.02.23 17:55, David Dima wrote:
> > Hi Marcus,
> > According to Galileo's signal plan
> > (https://gssc.esa.int/navipedia/index.php/Galileo_Signal_Plan
> >
> <https://gssc.esa.int/navipedia/index.php/Galileo_Signal_Plan>),
> E5b bandwidth is  25MHz,
> > but to save memory and resources, I sample at 20MHz because
> I demonstrated by testing that
> > is enough to process the signal without losing information.
> >
> > Regarding the Xlating filters: if I tune the USRP in the
> middle of the signals (1164MHz +
> > (1215-1164)/2)MHz = 1189.5MHz) , then I have to shift the
> spectrum +- 15.345 (According to
> > Daniel: "The band plan you posted is slightly wrong. The
> distance between the
> > AltBOC sidebands and the centre frequency is 15 * 1.023
> MHz.") to be able to record at
> > 25MHz each band (E5a and E5b). I am trying to do the following:
> > imagen.png
> > Kind regards,
> > David
> >
> > El mar, 28 feb 2023 a las 17:25, Marcus Müller
> (<mmueller@gnuradio.org
> > <mailto:mmueller@gnuradio.org>>) escribió:
> >
> >     Hi David,
> >
> >     On 28.02.23 17:17, David Dima wrote:
> >>     Dear Marcus, all
> >>     Thank you for your response. You are right, I will try
> to better explain the problem:
> >>
> >>     Well, when I record the signals separately (for example
> E5b) as shown in the below
> >>     picture, and after that I try to process the file
> containing the IQ samples by means
> >>     of GNSS-SDR free-tool, I can parse the messages to
> generate ephemeris, almanac or
> >>     Rinex files. Even if E5b bandwidth is 25MHz, it works
> sampling at 20 MHz.
> >>     imagen.png
> >
> >
> >     You're losing 1/5 of the relevant spectrum. That doesn't
> mean it *can't* work, it's
> >     just unnecessarily bad – honestly, **why** are you using
> a sampling rate that's not
> >     fit to represent the *full* signal? Can you please state
> *reasons*?
> >
> >
> >>
> >>     The issue comes when I try to record both signals at
> the same time. Taking into
> >>     account the suggestions Jim, Daniel and you have given
> me in the forum, I have made
> >>     a couple of changes in the program resulting in:
> >>     imagen.png
> >>     Now, at least I think I am closer to getting what I
> need but I am not sure if there
> >>     are more mistakes in the flowgraph. So, I have tried to
> record the signals according
> >>     to the above flowgraph but after that I still cannot
> read any signal from the
> >>     satellites whereas if I record them separately I can.
> >
> >     This makes no sense at all. Where do your "Center
> Frequencies" in the Freq.-Xlating
> >     filters come from?
> >
> >     Best regards,
> >     Marcus
> >
>