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Homework Help: Transfer Function: Magnitude and Phase of Complex Function

  1. Aug 28, 2012 #1
    1. The problem statement, all variables and given/known data

    f(s) = f([itex]\sigma[/itex] + j[itex]\omega[/itex]) = [itex]\frac{1}{(1+s)^2}[/itex]

    Find the magnitude and phase angle of f(j[itex]\omega[/itex])

    2. Relevant equations

    s = j[itex]\omega[/itex] is a substitution you can make, but I'm not sure if you are supposed to apply that here

    3. The attempt at a solution

    I tried substituting [itex]\sigma[/itex] + j[itex]\omega[/itex] into the function and applying s = j[itex]\omega[/itex].

    Then I get

    [itex]\frac{1}{(\sigma + 1)^2 + 2s(\sigma + 1) + s^2}[/itex]

    I have a feeling it's supposed to be a quadratic pole, but the form of this doesn't match the form of a quadratic pole exactly.
  2. jcsd
  3. Aug 29, 2012 #2

    rude man

    User Avatar
    Homework Helper
    Gold Member

    If they ask for f(jw) and they give you f(σ + jw) then σ = 0. So yes, let s = jw and proceed.
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