Re: [Discuss-gnuradio] Squelch block, AGC function and scanner example

[Martin Dvh]

Frank Brickle wrote:
> Martin Dvh wrote:
>
>  > I hope also to find a way to determine what kind of signals they are 
> (FM, AM, TV, FSK)
>  >
>  > This way you get a list of everything there is to receive with your 
> current frontend.
>
> A non-trivial task. Robust classification in this setting means doing 
> selective channel downconversion and making repeated sequential spectral 
> observations on the channels.
I was thinking of the following:
Find parts of the spectrum that are significantly above the noise level (peaks) 
and add these to a list.
After that process them one at a time (estimate bandwidth and do selective 
channel downconversion)
Then try AM-demod, FM-demod, (LSB-demod, USB-demod)
If one of these has a outputlevel above a certain threshold then mark it as 
AM-like, FM/FSK-like etc.
All of this does not have to be in realtime. Just save the 
powerspectra/original signal and process them later.

> In broadband, this usually requires maintaining a substantial delay line 
> from which to grab and process the selected channels. In commercial 
> systems like the Agilent E3238S the delay line has been the one of the 
> most expensive components.
>
> If you're interested, I wrote a brief expository article about automatic 
> signal classification using probability models of power spectra that 
> appeared in the December 2003 QEX.
Thanks for the tip.
Do you know if QEX is available in europe. (I live in the Netherlands)?
If I order a back-issue-article from the united states it takes a while to get 
here and shipping costs tend to rise.

Greetings,
Martin