Unobtainable bode plot ?

Hi,

I am using the bode( and margin( functions. (both are used to make Bode plots)

The issue I am having is with getting the proper "Matlab" form for plotting. it is given here

http://i.imgur.com/tVToE.png

since i would like to plot the bode plot, matlab needs the transfer function to be in terms of s. in my case, s = j*w_n. However, in the denominator of my transfer function, there is a dependency on 1/(w_n)^2. Using the tf( call convention, i do not believe i can input this transfer function based on what i know.

Does anyone know a way to solve this, or a different way to plot without using tf(? I could not find an obvious way to rewrite and simplify the equation in a form that would satisfy matlab, but at the same time, i highly doubt that it would be "impossible" to plot this.

thanks for all suggestions.

Answer 1

[Craig]

You might want to try this

(j*w_n)^2 = -w_n^2

then you can rewrite the w_n^2 term.