Re: [Discuss-gnuradio] FFT Spectral smoothing]

[Trond Danielsen]

2007/6/29, Aadil Volkwin <address@hidden>:
> Hi,
>
> My apologies for the lengthy silence. I have been out of town and unable
> to respond to mail.
>
> I'm not entirely clear on what you mean when you ask if the smoothing is
> over time or frequency.
>
> In essence, I would like to reproduce an output comparable to that of a
> spectrum analyser.
>
> That is, the GNU FFT show the frequencies and their related power in dB
> respectively, instantaneously.
>
> I would like to average the values of the Power spectrum and obtain an
> output showing the "smoothed/average" frequency values over a certain
> period. for instance say 100 samples of each frequency. Such that the
> values outputted are more stable and accurate and less eratic.
>
> As I am new to GNU_RADIO, I am not aware if the functionality for
> smoothing is built in and If I would need to write code to do this
> averaging of values, i'm not quite clear on where to begin.
>
> My apologies again for the lengthy delay and look forward and appreciate
> your assistance regarding this matter.
>
> regards,
>
> Aadil Volkwin

You can use the single pole iir filter to smooth the signal. The
single pole filter is also known as a exponential moving average
filter. You can find the GNU Radio documentation for it here:
http://gnuradio.org/doc/doxygen/classgr__single__pole__iir__filter__cc.html

If you want to know more, I can recommend this:
http://www.dspguide.com/ch19/2.htm

--
Trond Danielsen