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Re: [Discuss-gnuradio] Periodic averaging

From: Martin Braun
Subject: Re: [Discuss-gnuradio] Periodic averaging
Date: Tue, 9 Aug 2011 10:06:05 +0200
User-agent: Mutt/1.5.20 (2009-06-14)

On Mon, Aug 08, 2011 at 04:54:29PM -0400, Prachi Parihar wrote:
> Thanks for your response Marcus. I have been working with this block, but
> unfortunately, I do not want to iir filter the power spectrum. I want each
> spectrum to be weighed equally. I'd like to compute the arithmetic mean for 
> all
> the power spectra within a minute (I believe there are 4000 per second) so 
> that
> means I want to average 240,000 spectra and return a single power spectrum
> (which is the average) to be displayed. 

You can calculate this with the spectral estimation toolbox

Use the 'Welch' estimator. You can configure it to meet your needs

Have fun,

> As for the "keep one in N" file dump, I considered that when I came across
> moving_average_ff but that calculates the average every time it receives a new
> spectrum which is very wasteful in my case, since it's computing the average
> 240,000 times more than I need to.
> On Mon, Aug 8, 2011 at 12:45 PM, Marcus D. Leech <address@hidden> wrote:
>     On 08/08/2011 12:31 PM, Prachi Parihar wrote:
>         Hi everyone, 
>         I'm new to gnuradio and I was wondering if someone could point me in
>         the right direction. I'm using a usrp to read signals in the frequency
>         domain. I've been able to do this successfully using uhd_fft.py which
>         uses fft_sink_c() to display the signal. 
>         What I want to do instead of displaying the signal continuously is to
>         display the average of the power spectrum of the signal every minute
>         using all the samples collected in one minute. I can't find a block
>         that simply takes the (boxcar) average of many spectra once every
>         minute. 
>         If I can't find a block to do this, I will attempt to write one 
> myself.
>         If I need to, is there a strong need to write this block in C++ or
>         could I write it in python? 
>         Thanks in advance for your help, 
>         Prachi
>         _______________________________________________
>         Discuss-gnuradio mailing list
>         address@hidden
>         https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
>     There's a logPowerFFT hier block in GRC that allows you to set the frame
>     rate and "alpha" value, and it produces a FLOAT vector that's
>       the length of the FFT.
>     You can then further IIR filter those vectors, and then do a "keep one in
>     N" to make them dump to a file once per minute.
>     _______________________________________________
>     Discuss-gnuradio mailing list
>     address@hidden
>     https://lists.gnu.org/mailman/listinfo/discuss-gnuradio

> _______________________________________________
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Karlsruhe Institute of Technology (KIT)
Communications Engineering Lab (CEL)

Dipl.-Ing. Martin Braun
Research Associate

Kaiserstraße 12
Building 05.01
76131 Karlsruhe

Phone: +49 721 608-43790
Fax: +49 721 608-46071

KIT -- University of the State of Baden-Württemberg and
National Laboratory of the Helmholtz Association

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