[Discuss-gnuradio] Re: Frequency shift in the received and generated signals of the USRP

[Bruhtesfa Ebrahim]

 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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