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From: | David Dima |
Subject: | Re: Galileo Frequency Shifting and Filtering |
Date: | Tue, 28 Feb 2023 18:33:17 +0100 |
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:Thank you very much to everybody!Best regards,DavidEl 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
>
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