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Signal not neriodic if multiplied by decaying exponential?

  1. Sep 18, 2010 #1
    The signal [tex] x(t) = e^{jt} [/tex] is periodic.

    The signal [tex] x(t) = e^{-t}e^{jt} [/tex] is not periodic.

    The decaying exponential makes the complex exponential decay and converge toward zero, but why is it not periodic?

    Also, this signal is not considered time limited since it never actually reaches zero. Right?
     
  2. jcsd
  3. Sep 18, 2010 #2
    Because you can't find a real T such that x(t)=x(t+nT).
     
  4. Sep 18, 2010 #3
    Neat. I was thinking about this qualitatively and forgot about the required condition you mentioned.

    Thanks.

    Is what I said about it not being time limited correct?
     
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