How to compute the value in one point through the transferfunction?

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tqy 2012-9-19

Dear all,

I has a transferfuntion H(s), I want to know the amplitude and phase in a particular point, for expample, if s = 1+j.

I don't know how to do this , can anybody help?

Thanks a lot~~~

Honglei Chen 2012-9-19

编辑：Honglei Chen 2012-9-19

First of all, please delete duplicate thread. Second, your question is not clear. You have H(s), isn't it just plug 1+j into it?

tqy 2012-9-20

I'm sorry for the duplicate thread, I have already deleted it.

Yes, I have H(s), I don't how to plug 1+j into it, use function "subs"? It seems doesn't work.

The type of H(s) is "tf", with the Laplace variable "s", so my question is how to replace "s" with "1+j". Any function can do this?

Thank you.

Honglei Chen 2012-9-20

I think the following is what you mean.

s = tf('s')
H = s/(s^2+2*s+10)
evalfr(H,1+1i)

tqy 2012-9-21

Thank u very much! That's what I want.

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