# How do I draw the Bode plot of this?

#### StuckStudent123

Joined Sep 23, 2016
23
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I have seen the answer with Matlab but the only thing I'm struggling with is the root at -0.5+/-0.5i. Would anyone be able to tell me how to account for this?

Edit: What I find confusing about the root is that it's complex. I saw in a video online that when it's complex the magnitude has a spike but Matlab doesn't show this spike.

Joined Mar 10, 2018
4,057
I saw in a video online that when it's complex the magnitude has a spike
Not necessarily true, depends on Re losses compared to energy storage in L & C.

Regards, Dana.

#### StuckStudent123

Joined Sep 23, 2016
23
Not necessarily true, depends on Re losses compared to energy storage in L & C.

Regards, Dana.
Thanks,
Would you be able to tell me how you know where along to x axis the complex pole needs to be? Is it its magnitude?

Joined Mar 10, 2018
4,057
A bode plot is a magnitude plot, axis freq and magnitude, whereas a pole zero plot has
a Real axis and an Imaginary axis. So on a bode plot you are plotting the magnitude
of Z or V or I for the transfer function. You can plot the effect of a single pole or zero
on Bode, its magnitude at specific frequencies.

The pole plot has a Re and Im part, real and imaginary axis, that you plot, as follows -

Regards, Dana.

#### drc_567

Joined Dec 29, 2008
1,156
Try arranging the quadratic factor in the form:
$${s^2+2\zeta\omega_ns+\omega_n^2}$$

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