On 07/17/2014 01:05 AM, Stefan Oltmanns wrote: > Thank you very much for the fast answers! > The signal I attached in the last message is generated by a µC and then > a lowpass is applied (not just RC, but two op-amps). In another mic type > the signal is generated by changing the reference frequency (a varicap > controlled by the µC is connected to the main crystal). > > What exactly does mix to zero mean? From what I understood so far, > I=RF*cos(ωt) and Q=RF*sin(ωt), when I set ω=0 => I=RF and Q=0 is that > what you mean?
No, that would still be a real signal. In your nomenclature, if ω=10Hz * 2\pi, then you get a complex signal (10 Hz being what you said was the center frequency of the battery signal). > I changed the filter settings and now the dip between two blocks is more > precise. I attached two signals generated by the different microphone > types using the same protocol. I tried the quadrature_demod, but result > especially for the varicap-mic seems not be useful (also tried changing > the only parameter). To understand what's going on, I recommend you generate an FSK signal in GRC and then use quadrature_demod and see what happens. > I think what I have to do is measure the distance between two peaks > (only positive, threshold 200u): > Distance more than 0,5s -> New Block starts > Distance between 0,3s and 0,4s -> 1 > Distance between 0,15s and 0,25s -> 0 > else -> reset (delete buffer and wait for new block start) > Can this be done with GnuRadio? Hm, this sounds too much like guesswork. Do you have a spec sheet or something describing the modulation in more detail? M > > Best regards > Stefan > > Am 16.07.2014 15:43, schrieb Marcus Müller: >> Ahh-- my mistake, I was assuming the "dips" were something like one >> symbol, the other being the continous wave with the 400u amplitude, and >> completely missed the differences in period on the non-dippy signal... >> The lower halfwaves of the lower-frequency oscillations look a little >> strange; maybe this signal was generated by RC-lowpassing a PWM signal? >> >> >> On 16.07.2014 15:18, Martin Braun wrote: >>> On 07/16/2014 03:08 PM, Marcus Müller wrote: >>>> this doesn't look like FSK, because then the amplitude of the >>>> oscillations shouldn't change (only their frequency). >>>> If I had to guess, it would be on-off-keying, and you could simply >>>> detect that by squaring the signal, and using the integrate block on >>>> that, with a integration length amounting to your symbol duration in >>>> samples, which might be a little hard to guess from the signal you >>>> posted, but maybe you know the symbol rate from elsewhere, or can >>>> determine it by comparing signals from different battery states? >>> The dips might also be between bursts -- it does look a bit like FSK, >>> but hard to say. >>> Stefan: If you mix this down to zero, your signal will be complex anyway >>> (radio signals are also always real, but we don't care :D ). Then you >>> can put it into a quadrature_demod_cf. >>> Question is, how do you synchronise? Maybe you can use those dips to do >>> that... Or maybe the symbol timing is well defined, then it's easier. >>> >>> M >>> >>> >>> >>>> Greetings, >>>> Marcus >>>> >>>> On 16.07.2014 14:51, Stefan Oltmanns wrote: >>>>> Hello, >>>>> I would like to write an application that checks the battery status >>>>> of wireless microphones. The battery status is transmitted as a >>>>> very low frequency (below 10 Hz) signal that is mixed in the normal >>>>> audio. I was able to filter the signal out of the demodulated audio >>>>> and display it (see image). AFAIK this modulation is called FSK. >>>>> The signal that is shown there should decode to data-blocks >>>>> containing "11100000000" or something like that, are there any >>>>> blocks in GnuRadio that can do that? Because the signal is derived >>>>> from audio it is not complex but normal float, all GnuRadio >>>>> demodulators seem to work only on complex data. Can somebody please >>>>> help me? >>>>> Best regards, Stefan >>>> >>>> >>>>> _______________________________________________ Discuss-gnuradio >>>>> mailing list Discuss-gnuradio@gnu.org >>>>> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio >>>> >>>> _______________________________________________ >>>> Discuss-gnuradio mailing list >>>> Discuss-gnuradio@gnu.org >>>> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio >>>> >>> >>> >>> >>> _______________________________________________ >>> Discuss-gnuradio mailing list >>> Discuss-gnuradio@gnu.org >>> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio >> >> >> >> >> _______________________________________________ >> Discuss-gnuradio mailing list >> Discuss-gnuradio@gnu.org >> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio >> > > > > _______________________________________________ > Discuss-gnuradio mailing list > Discuss-gnuradio@gnu.org > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio > _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
