Forum: GNU Radio FFT Spectral smoothing

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Aadil V. (Guest)
on 2007-06-21 17:40
(Received via mailing list)
Hi,

i'd like to do spectral smoothing on an FFT in real time through
GNU_RADIO.

Is there a function that will allow me to do this in the GNU_RADIO
modules?

If not has anyone attempted it before, or have any suggestions as to how
I should go about implementing it myself.

Perhaps any ideas of cascading blocks that do exit.

Thanks,

Aadil
Trond D. (Guest)
on 2007-06-21 19:05
(Received via mailing list)
2007/6/21, Aadil V. <removed_email_address@domain.invalid>:
>
> Perhaps any ideas of cascading blocks that do exit.
>
> Thanks,
>
> Aadil

>From what I can find, "spectral smoothing" is not an unambiguous term.
Could you please elaborate the problem, preferably the mathematical
definition of what you are trying to accomplish.

Best regards,
--
Trond D.
Johnathan C. (Guest)
on 2007-06-22 21:21
(Received via mailing list)
Aadil V. wrote:

> i'd like to do spectral smoothing on an FFT in real time through
> GNU_RADIO.
>
> Is there a function that will allow me to do this in the GNU_RADIO
> modules?

Are you referring to smoothing FFT bins over time or over frequency?

--
Johnathan C.
Corgan Enterprises LLC
http://corganenterprises.com
Peter M. (Guest)
on 2007-06-22 22:10
(Received via mailing list)
>> i'd like to do spectral smoothing on an FFT in real time through
>> GNU_RADIO.
>>
>> Is there a function that will allow me to do this in the GNU_RADIO
>> modules?
>>
>
> Are you referring to smoothing FFT bins over time or over frequency?
>
>

I guess he means time.  This would greatly improve
the FFT demos, since currently there is no "video
filtering", as the spectrum analyzer folks say.

A more flexible spectral estimate would allow showing
nice clean noise floors at the expense of a little
measurement time.

Cheers,
Peter M.
Johnathan C. (Guest)
on 2007-06-22 22:25
(Received via mailing list)
Peter M. wrote:

> I guess he means time.  This would greatly improve
> the FFT demos, since currently there is no "video
> filtering", as the spectrum analyzer folks say.

In the current FFT demo, it is possible to right-click on the display
and select 'Average'.  This will perform low-pass filtering on each FFT
bin such that the "noise" averages to its rms value but the signal peaks
 remain.  This is done in the flow graph by using a
gr.single_pole_iir_filter as an exponential averager.  You can do this
in the waterfall mode as well.

--
Johnathan C.
Corgan Enterprises LLC
http://corganenterprises.com
Lamar Owen (Guest)
on 2007-06-22 23:18
(Received via mailing list)
On Friday 22 June 2007, Johnathan C. wrote:
> Aadil V. wrote:
> > i'd like to do spectral smoothing on an FFT in real time through
> > GNU_RADIO.
> >
> > Is there a function that will allow me to do this in the GNU_RADIO
> > modules?
>
> Are you referring to smoothing FFT bins over time or over frequency?

General smoothing over time and frequency would be great; smoothing over
time
is doable now with averaging.
--
Lamar Owen
Chief Information Officer
Pisgah Astronomical Research Institute
1 PARI Drive
Rosman, NC  28772
(828)862-5554
www.pari.edu
Matt E. (Guest)
on 2007-06-23 00:25
(Received via mailing list)
Peter M. wrote:
>>
>
> I guess he means time.  This would greatly improve
> the FFT demos, since currently there is no "video
> filtering", as the spectrum analyzer folks say.
>
> A more flexible spectral estimate would allow showing
> nice clean noise floors at the expense of a little
> measurement time.

If you right-click in the spectrum window you will see an option for
averaging and peak-hold.

Matt
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