[Discuss-gnuradio] Re: how to find local peak of sinc function ? peak detector setup ?

[Patrick Strasser]

schrieb grc007 am 2010-06-17 23:28:
> Hello,
> I need again your help for this problem:
> - I want to locate the peaks (local maximum) of the input signal, which is
> sinc-function pulse (the 2 gray points in picture sincpuls.png, not the
> neighbour peaks).
> How can I use the gr_peak_detector in grc to do this ?

If you know the exact shape of the signal you want to detect, you may 
get better results with doing a correlation with the desired signal 
first. Then you can use a threshold or a more sophisticated peak detector.

> - If you look at my grc-picture (peakfalse.png) you will see that the peaks
> are not at the right places. They happen before the true peaks of the
> sine-function.

You did not show the complete flow graph in your pictures, but chances 
are good that its not early, but late.

Both the FFT sink and the peak detector need some time for processing 
reulting in some delay so you must not expect their output to be synced. 
You need to find out somehow both delays, or at least the difference of 
the delay. Try you flowgraph with other imput signals, like ramp.

Patrick

--
Engineers motto: cheap, good, fast: choose any two
Patrick Strasser <patrick dot strasser at tugraz dot at>
Student of Telemati_cs_, Techn. University Graz, Austria