Re: [Discuss-gnuradio] Periodic averaging

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
https://www.cgran.org/wiki/SpecEst.

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

Have fun,
MB

>
> 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 <mleech@ripnet.com> 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
>
>
>
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>
> 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.
>
>
>
>
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