Hi,
I’m an engineer from Spain and I’m interested in a GSM receiver because I would like to study the internal signals for a research project. In particular, I’m interested in the analysis of the IF signal, but, as Alexander told me, the LMS6002D uses zero-IF architecture, so there is no real "IF" signal, there is only baseband signal.
Well, they also have a optional GSM front end board that has an IF. However it has a very narrow IF filter since the goal was to about in-band interference from neighbour channels ...
I guess I could also use this signal for my purposes, but only if all 124 GSM channels can be found at that point. I’m not sure if this is possible, since there is a low-pass filter before. Does anybody know if I can extract that information, that is, the analogic 124 channels after the RF mixer?
The filters can be set to 28 MHz wide and the LMS has analog I/Q debug outputs, so yes you could get the analog out. But it's I/Q not a single signals so you'll need two fast ADC to get it digitized.
OTOH why wouldn't you just use the ADC in the LMS ? They're clocked at 26 Mhz (or could even be fed higher frequency) and so you should be able to get the whole 25 MHz of P-GSM band.
Cheers,
Sylvain