Author Topic: Filter selection Spectrum Analyser FFT  (Read 2056 times)

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Offline ramjet1953

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Filter selection Spectrum Analyser FFT
« on: October 07, 2013, 04:35:21 am »
I wonder if Dave can give us a lecture on filter selection when using FFT with a spectrum analyser?

My virtual oscilloscope/spectrum analyser has a confusing list of selections.

Rectangle, Bartlett, Triangular, Cosine, Hanning, Bartlett-Hanning, Hamming, Blackman, Blackman-Harris etc. ad nauseum.
I looked around, but have yet to find an article detailing selection criteria.

It would be great to know which filter is the best choice for different situations.

Regards,
Roger
 

Offline olepr01@gmail.com

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Re: Filter selection Spectrum Analyser FFT
« Reply #1 on: October 07, 2013, 08:22:39 am »
That would be the window-function applied prior to performing the FFT, not a "filter" as such; http://en.wikipedia.org/wiki/Window_function, also http://www.ni.com/white-paper/4844/en/
« Last Edit: October 07, 2013, 08:24:34 am by olepr01@gmail.com »
 

Offline MarkL

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Re: Filter selection Spectrum Analyser FFT
« Reply #2 on: October 09, 2013, 01:06:16 am »
Although somewhat specific to Tek equipment, this paper has some good general info about the commonly implemented FFT window types:

  http://www.tek.com/document/application-note/fft-applications-tds

Also from Tektronix, in the TDS3xxx FFT user manual, is a simple chart that summarizes situations where you would select one window type over another (page 12/13):

  http://www.tequipment.net/pdf/tektronix/TDS3FFT_UserManual.pdf

(Just to be clear, the various window types apply to anyone's implementation, not just Tektronix...)
 

Offline w2aew

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Re: Filter selection Spectrum Analyser FFT
« Reply #3 on: October 09, 2013, 01:29:10 am »
My friend Ian wrote a short blog on the topic of these window functions.
http://www.tek.com/blog/window-functions-spectrum-analyzers
YouTube channel: https://www.youtube.com/w2aew
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Offline ramjet1953

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Re: Filter selection Spectrum Analyser FFT
« Reply #4 on: October 09, 2013, 01:37:06 am »
Hi, Guys!  :)

Thanks for the replies and links.
After reading all of the links, I feel a lot more confident which flavour to choose.  :-+

Regards,
Roger
 


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