On 6/20/06, Piotr Majdak piotr@majdak.com wrote:
Hi chucck,
Chuckk Hubbard wrote:
On 6/20/06, Piotr Majdak piotr@majdak.com wrote:
Writing the original signal and the real and imaginary parts of the output to graphs shows lots of alterations. It is fine with a block containing an integer number of cycles, but otherwise gets weird results. See attached.
Every time you write the signals to the tables, the phase of the original signal changes. Because of the windowing effects the processed signal (FT->Re{}->IFT) changes dramatically: the real part of the FT result contains the information about the symmetric part of the original signal (=cosines), which changes with its phase.
So it doesn't work. I mean, I understand, with a rectangular window there are discontinuities that read as crazy frequencies, but essentially this doesn't work for supplying the imaginary part. I guess it's just academic now, but I'm still curious.
-Chuckk
Thanks for the nice example - it took me a while to analyze what happens here.
br, Piotr
-- Piotr Majdak Institut für Schallforschung Österreichische Akademie der Wissenschaften Reichsratsstr. 17 A-1010 Wien Tel.: +43-1-4277-29511 Fax: +43-1-4277-9296 E-Mail: piotr@majdak.com WWW: http://www.kfs.oeaw.ac.at
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