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