0
$\begingroup$

I am a newbie in signal processing. I am testing the Hanning window on a signal. Obviously doing this window also means cut some energy of the signal, and when I do the DFT, the 0 frequency is not equivalent anymore to the average of the time history. Do you usually solve in some way this problem? Can someone suggest papers or books where noise-reducing strategies for the FT of a signal are investigated? I just don't know how to start, an online search didn't give me more than basic definition (so please don't send me the Wikipedia definition of the tapering window)

Best

$\endgroup$
3
  • $\begingroup$ Hm, I find difficult to relate Hanning window, the DC frequency, and noise reduction in the frequency domain. What kind of signals are you dealing with? $\endgroup$
    – GKH
    Jan 19, 2020 at 15:03
  • 2
    $\begingroup$ In a nutshell, you must normalize the energy by the energy of the window. In case of simple magnitude, this means dividing by the sum of window samples. This publication has great explainations. $\endgroup$
    – jojek
    Jan 19, 2020 at 15:03
  • 1
    $\begingroup$ Excellent reference, thank you for reminding me it is in my "to read in a serious manner" list for a while $\endgroup$ Jan 19, 2020 at 15:15

1 Answer 1

1
$\begingroup$

I suspect you are talking about the Hann window, after Julius von Hann, and Blackman & Tukey. Of course, a non-constant window may induce energy variations, either used as a weighted average, or a convolutional filter. This can be compensated in several ways:

  • by normalizing the window amplitudes
  • by separating tipme-portions, or signal components, like removing the mean or low-frequencies before doing the processing
  • by modelling the signal and applying model-based corrections.

More would be needed on your signal to provide more precise answers. R. Lyons on a diagram on page xviii of his book Understanding Digital Signal Processing highlights the importance of windows.

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct.

Not the answer you're looking for? Browse other questions tagged or ask your own question.