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I'm looking at this example here, and am using the additive method to plot my bode plots.

To help me draw more accurate plots, I was wondering whether there is an easy way to find all $0 dB$ points?

Doing this question for example:

$H(s) = -10\frac{s}{(s+1)^2 (\frac{s}{10} + 1)}$

I'd need to find all points where $|H(s)| = 1$

so I compute $|H(s)| = |10| \frac{w^2}{(w^2 + 1)\sqrt{0.01w^2+1}} = 1$ which is not easy to solve at all.

How do I go about doing this?

Louis93
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    Why would finding the points with magnitude 1 help with creating a more accurate bode plot? These points depend on the overall scaling factor (20 in your case), which doesn't influence the shape of the plot at all, just its position relative to the 0dB line... – fgp Feb 18 '14 at 13:46
  • Since 20 log mag 1 = 0? And the w at which this occurs would be your intercept, correct? – Louis93 Feb 18 '14 at 14:52

1 Answers1

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You should look at it as f1=s f2 =1/(s+1)^2 f3=1/(0.1s+1) then tou graph each by itself and because it is linear you just attach the lines. You will be able to see where is the zero

hope this helps. Nachum

user1
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    For more complex Bode plots, it will be difficult to pinpoint the w axis intercepts using hand drawn approximations. To be certain, you may have to plug your w into yr magnitude equation several times – Louis93 Feb 18 '14 at 14:55