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Homework Help: Get transfer function from bode plot

  1. Jul 29, 2012 #1
    1. The problem statement, all variables and given/known data
    What is the transfer function described by this bode plot:
    http://img96.imageshack.us/img96/4775/capturegib.jpg [Broken]
    *The answer is 3s, but I don't know where it comes from.

    2. Relevant equations

    3. The attempt at a solution
    Correct me if I am wrong. A bode plot is a combination of 2 plots, one is dB vs. w, the other one is angle vs. w. Each linear transfer function can be breakdown into 7 types of component to be represented on a bode plot. The answer to this problem is "3s", suggesting that it is the differentiator type. For differentiator with w=3, its bode plot has a slop of 20dB/dcd and intercept at w=3 (dB vs. w graph), and an angle of constant 90 degree (angle vs. w graph). I don't see any of the characteristics on the given diagram. I can see that the two plot has been combined into one, but how exact do I interpret such diagram and be able to come up with 3s as the transfer function? Thank you so much!
    Last edited by a moderator: May 6, 2017
  2. jcsd
  3. Jul 29, 2012 #2
    Nevermind, I think I got it. Thanks.
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