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
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