Understanding Digital Filters

Discussion in 'General Electronics Chat' started by nanobyte, Aug 14, 2007.

  1. nanobyte

    Thread Starter Senior Member

    May 26, 2004
    118
    1
    In a book I read ("Digital Signaling Processing" by Steve White) there is a concept that I am having a hard time grasping. Why do digital filters repeat their gain characteristics past the folding frequency?
     
  2. Papabravo

    Expert

    Feb 24, 2006
    10,145
    1,791
    Because they can't tell the difference between the frequencies. The higher frequencies alias and are indistinguishable from the lower frequency.
     
  3. Dave

    Retired Moderator

    Nov 17, 2003
    6,960
    144
    Without delving into the details of it, it is a consequence of the discrete Fourier transform. As Papabravo says, they are indistinguishable but very real frequency components and should be dealt with when processing such signals.

    Dave
     
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