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Different FFT Windowing types / How to use / Example Screenshots

Depending on the signal you wish to measure you should choose the right FFT windowing type otherwise you might get a wrong amplitude measurement or could even miss a signal.

In most cases the Hann or Flat Top Windowing works fine (default setting).

A comparrison of some FFT windows is shown in attached scrennshots using a single tune CW signal.

Some selection help is seen in below table but these are just a few of the possible window functions. There is no universal approach for selecting a window function. However, the table below can help you in your initial choice. Always compare the performance of different window functions to find the best one for the application.

Hann

  • Unknown content
  • Sin wave or combination of sin waves
  • Narrowband random signal (e.g. vibration data)

Flat Top

  • Sin wave (amplitude accuracy is important)
  • Accurate single tone amplitude measurements

Uniform

  • Broadband random (white noise)
  • Closely spaced sin waves
  • Two tones with frequencies close and almost equal amplitudes

Hamming

  • Closely spaced sin waves

Kaiser

  • Two tones with frequencies close but amplitude very different
Uploaded files:
  • FFT-Windowing-Comparison-Bins.jpg
  • FFT-Windowing-Comparison-Cubic.jpg