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Matlab Control Systems Question

  1. Apr 3, 2006 #1
    I am having a problem with plotting Bode plots in Matlab. We are required to plot a e^(-sT) (simple time shift) as a Bode plot. The "bode" function in Matlab requires either a TF, ZPK, SS, or FRD system as its first input. I cannot seem to find out how to plot the exponential. I can easily plot the normal transfer functions however. If anyone has any idea that would be great.

    Stephen McFetridge
    University of Alberta
  2. jcsd
  3. Apr 8, 2006 #2


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    Define a frequency vector, for instance:
    omega = 0.1:0.01:10
    % omega goes from 0.1 rad/s to 10 rad/s by steps of o.o1 seconds.
    Then define your function
    H = exp(-i*omega*T)
    where T is the known delay
    The amplitude in dB is:
    Amp = 20*log10(abs(H))
    and the phase in radians
    Phase = angle(H)
    Now you can draw the Bode plots as
    semilogx(omega, Amp)
    semilogx(omega, Phase)
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