The spectrum looks clean so probably the LPF is not requirered. I just got my hands on a USRP board and started playing with it for fun. If I came to something interesting (i.e. complete GSM modulator) I will contribute it to the project.
Thks again and Rgds, On Thu, Apr 17, 2008 at 11:26 AM, Brian Padalino <[EMAIL PROTECTED]> wrote: > On Thu, Apr 17, 2008 at 11:11 AM, Wireless Monster > <[EMAIL PROTECTED]> wrote: > > Brian, Dan, > > > > It is working now. Thanks again for your help. > > > > One more basic "signal processing question" ... knowing that the input > and > > output are complex (GMSK modulated signal), should I use complex or real > > coefficients for the resampler filter (rational_resampler_ccc, vs. > > rational_resampler_ccf) ? > > I wouldn't use a ccf. I'd either use an fff on each the real and > imaginary portions of the signal, or I'd use a ccc on the combined > signal, but that's just my own personal opinion. > > > Regarding Ed, question on the LPF after the resampler, I am not sure... > it > > does not seems to be needed... any clue? > > Look at the spectrum coming out of your rational resampling filter and > make sure there are no spurs or images outside the intended band. > That's probably the easiest thing to do, though I don't think there is > a need. The source for the filter is located here: > > > http://gnuradio.org/trac/browser/gnuradio/trunk/gnuradio-core/src/lib/filter/gr_rational_resampler_base_XXX.cc.t > > There is a little bit of python taking place to actually generate the > code for all the filter types, but you can get the general idea of how > it works. > > On a side note, do you have a GSM modulator that you are thinking of > contributing to the project? Or is this strictly for personal > purposes? > > Brian >
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