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Bode plot

  1. May 23, 2014 #1
    hey guys,

    i have a question regarding bode plot

    g(s)= 1/(s2+4)

    i did get the magnitude plot correct but i am unable to understand the phase plot. by calculating on paper i got 0° but in matlab it changes from -360° to -180°

    i havent understood how the initial phase is -360 which changed to -180 at the corner frequency(2)

    please explain. i would really appreciate if you could explain me how to draw the phase plot for second order system with ς‚= 0

    thank you in advance
  2. jcsd
  3. May 23, 2014 #2


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    Gold Member

    -360 degrees is equal to 0!

    Typically each pole will add a 90 degrees phase shift that begins 1 decade before the pole and ends one decade after. Since there are two poles the phase shift will be 180 degrees
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