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How is the periodogram defined? I have been searching the internet a lot, and I find two different definitions:

  • periodogram is the squared magnitude of the DFT
  • periodogram is the squared average of the DFT

which one is correct?

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up vote 4 down vote accepted

The periodogram is simply the squared magnitude of the DFT. Since the periodogram is a rather poor estimate of the power density spectrum of a random process there are methods which use averaging of periodograms to obtain better estimates of the power spectrum. Two such methods are Welch's method and Bartlett's method.

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