GSM-850

Sylvain Munaut 246tnt at gmail.com
Mon Aug 22 15:14:06 UTC 2011


Hi,

> This wouldn't explain why the C122 GSM-850/1900 needs the "I/Q-swap"
> for GSM-850 TX only.

Mmmm, indeed. The iota tx/rx IQ lines are separate but that would be
the same for all bands.

Maybe it's due to the RITA with it's "offset TX PLL" that sometimes
uses the left image and sometimes the right image of the signal  ?
(you can see that in the formula with 1/L - 1/M  vs 1/L + 1/M).

In this case maybe it should the 'RF' stage that should return if a
band should be swapped or not ?


> And if I remember, Harald tried it with a
> GSM-900/1800 phone on GSM-850 (of course there are filter
> issues in this case) and it required the "I/Q-swap" again
> for GSM-850 only.

Cheers,

     Sylvain




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