I have tried building the analytic by hilbert, but I think that, because of the many near DC components of the signal, I do not get a nice quadrature demod output...I will try with a pll, thanks for the suggestion!
MC > Matteo Campanella wrote: >> Hello, I am quite stuck at a problem, that is, how to demodulate a FM >> signal that is NOT in complex form using existing gnuradio blocks. The >> quadrature demodulator works only with complex input; I have tried to >> build an analytic signal out of my real one, but the result of the >> demodulation is then quite poor. > How did you try to "build an analytic signal out of my real one". > The easiest way of doing that is to use gr.hilbert_fc (numberoftaps) > The numberoftaps in combination with the samplerate determines the lowest > frequency for which the hilbert transform is accurate. > (The higher the number, the more accurate the transform) > Try and experiment with the numberoftaps value. > Most of the time a value like 256 will do. > > You can also try to use the usrp_wfm_pll.py example. > This one uses a pll to recover the frequency modulation which should > perform much better with a real source. > > The pll it uses is gr.pll_freqdet_cf > You could build a gr.gr_pll_freqdet_ff block to go straight from real data > to frequency detection. > > (You can look in the old code atsc/GrAtscFPLL.cc > This is the PLL which was used for atsc demodulation. It works with real > input data.) > Greetings, > Martin >> >> Any suggestions? >> Matteo >> >> >> >> _______________________________________________ >> Discuss-gnuradio mailing list >> Discuss-gnuradio@gnu.org >> http://lists.gnu.org/mailman/listinfo/discuss-gnuradio >> > > > _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
