FSK Demodulation with ADSR

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DBW

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Hi all,

I have a project in which I need to implement FSK communication with hydrophones.
Thus far, my plan is to implement noncoherent demodulation of the signal by passing the signal through bandpass filters and envelope detectors in a similar fashion to page 10.
If I were to use this demodulation scheme, would I be able to use the ADSR envelope?

I'm open to other demodulation schemes as well, bearing in mind that I shall implement chirp spread spectrum FSK in a high noise environment.

Thanks :)
 
Hi all,

I have a project in which I need to implement FSK communication with hydrophones.
Thus far, my plan is to implement noncoherent demodulation of the signal by passing the signal through bandpass filters and envelope detectors in a similar fashion to page 10.
If I were to use this demodulation scheme, would I be able to use the ADSR envelope?
No, because that's a generated/sequenced envelope. An envelope detector measures the envelope of a signal,
the AudioAnalyzePeak and AudioAnalyzeRMS classes in the Audio library each do a version of this, but at a granluarity
of the audio block size, and this isn't tunable.
I'm open to other demodulation schemes as well, bearing in mind that I shall implement chirp spread spectrum FSK in a high noise environment.

Thanks :)
Another approach is using FFT bins corresponding to the two frequencies, again issues of granularity need to be addressed.

Or write your own envelope detector that's aware of the carrier and modulation frequencies and is tuned to them for best
noise performance.
 
Thanks very much for your input! I'll look into using FFTs rather than envelope detection.
 
The ultimate approach to envelope detection would be to use a discrete Hilbert transform direct into a complex absolute-value
function, but that's overkill (although elegant and probably the "correct" way, mathematically)
 
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