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Homework Help: Question about system stability

  1. Apr 15, 2014 #1
    If a system transfer function has a pole equal with 1 , j, cos(pi/4)+j*sin(pi/4) in other words its location is on the margin of the unit circle, it`s the system stable? In my opinion it`s not stable because we have a sum of 1 which doesnt converge but im not sure. Everywhere ive read it says the poles must be inside the unit circle but it doesnt say anything about poles on the margin of the unit circle. Can somebody give me a precise answer? Thanks!
    Edit: Im referring to z-plane
  2. jcsd
  3. Apr 15, 2014 #2


    Staff: Mentor

    What does this (above) mean?
    What's the z-plane? Do you mean the plane z = 0?
  4. Apr 16, 2014 #3
    Iam talking about z transform and stability analysis.
    Like if H(z)=z/(z-1), pole is 1. is it stable?
    I have exam in 5 hours and i need an answer .
    Last edited: Apr 16, 2014
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