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From: "ggk " <ggkmath@comcast.net>
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Subject: Re: how to reverse windowing effect?
Date: Tue, 20 May 2008 22:33:03 +0000 (UTC)
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Dale, thanks... in your text

"Nuttall calls it the minimum 4-term window. The 
coefficients are given in (37) on page 89."

is (37) referencing a paper? Or is it just page 89 of the 
Nuttall paper I referenced above? 

Rune, thanks... I need to apply a window to separate the 
spurs from the random background noise. Then apply a 
bandpass filter to the result, take the inverse FFT, and 
reverse the effect of the window to get a real-time 
waveform to measure the PDF of zero-crossings (my ultimate 
goal). 

However, based on the response, it appears I'll need to re-
think my methodology to remove the random noise from the 
real-time waveform. Assuming my windowing allows me to 
identify the relevant spurs in the waveform, how can I use 
this information to re-create an accurate real-time 
waveform having only these spurs in it (and not the random 
noise)? Perhaps a real-time filter with bandpasses only at 
those spur frequencies identified by the windowing...? 

Any recommendation for a new methodology, as reversing the 
effect of the windowing seems to out of the question. I 
wonder if I could just throw out the edges of the real-
time waveform and use the center? (But I suspect the 
center is modified by windowing as well).