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

From: Patrick Strasser
Subject: [Discuss-gnuradio] Re: how to find local peak of sinc function ? peak detector setup ?
Date: Fri, 18 Jun 2010 17:03:35 +0200
User-agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; de; rv: Gecko/20100317 Lightning/1.0b1 Thunderbird/3.0.4

schrieb grc007 am 2010-06-17 23:28:

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

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.


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

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