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[Discuss-gnuradio] Re: Frequency shift in the received and generated sig
From: |
Bruhtesfa Ebrahim |
Subject: |
[Discuss-gnuradio] Re: Frequency shift in the received and generated signals of the USRP |
Date: |
Thu, 20 Nov 2008 16:16:53 +0100 |
Thanks Brian!
> Because each local oscillator is not exactly 64.000000000MHz, when
> that signal is multiplied up by the PLL - so does the "offset".
I see on "USRP under 1.5x magnifaying lens, by: Firras" that the
tranceiver osillators tune as close as possible to the desired receiving
frequency in steps of 4MHz,and the remaining frequency offset is
downconverted by the USRP DDC. So if I am tuning to 2.40GHz(multiple of
4MHz), why a frequency offset occurs? or could you discribe how the
desired RF signal at 2.40GHz ends up at around 12KHz for XCVR2450
tranceiver particularly?
> The fortunate part for you is that it is very well documented and
> written about extensively. Take a look in your favorite wireless
> communications systems book and you will most likely see a good
> discussion with regards to time synchronization.
Do you think this frequency offset remains exactly the same every time
for the same USRP at a constant target frequency(ex. 2.40GHz)? Or is it
time varing?
Also is there some way(GNU Radio code that uses PLL and the frequency
offset) to demodulate the signal at this offset frequency back to
baseband?
Bruhtesfa
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