On Wed, Jan 30, 2013 at 11:16 AM, Brian Padalino <bpadal...@gmail.com>wrote:
> > On Wed, Jan 30, 2013 at 9:30 AM, adream <adream...@gmail.com> wrote: > >> I am feel sorry for no reply > > > It's just been a day - sometimes if the answer doesn't come quickly, > people are confused by what you're asking. > True. A lot of us are also very busy with other things and can't come rushing to answer all questions. > > 2013/1/30 adream <adream...@gmail.com> >> >>> Does gnuradio provide this function? >>> thank you >>> >>> > Natively I don't think it does, but there are properties to the > demodulated signal you may be able to exploit and calculate it. > > >> >>> 2013/1/29 adream <adream...@gmail.com> >>> >>>> Hello, >>>> I am learning PM Demodulation, and someones tell me that the FM >>>> Demodulator in gnuradio can demodulate the PM signals. >>>> I want to get the carrier's frequency offset in PM demodulating, does >>>> gnuradio provide this function? >>>> For example, in my project, I set the frequency of IF signal is 70MHz, >>>> but the real input IF signal is 70.01MHz. >>>> In this case, I hope my program can print the carrier's frequency >>>> offset, 10KHz >>>> Thank you. >>> >>> > FM has the property that frequency offset results in a DC offset at the > demodulated signal that is proportional to the amount of frequency offset > (given the input signal has no DC component). > > For PM, since you are not taking the first derivative of the phase as you > are with FM, the DC component will be shifted up to your frequency offset. > Doing a long term average of a demodulated FM signal should (hopefully!) > come out to be 0 for no frequency offset. > > You could FM demodulate, put a DC filter then reintegrate at the output to > get your PM signal back - but I am not sure how well that works. Give it a > shot and let us know! > > Hope that helped. > > Brian > And remember, there are also the PLL blocks. Tom
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