Complex transfer function, 's' to 'jw' conversion

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mitra
mitra 2013-6-9
评论： lounis chehrit 2021-6-8
Hi,
I have a big size transfer function in S-domain and I need to replace the 's' with 'jw' in that function (conver s to complex mode). Can anyone help me?
  2 个评论
Azzi Abdelmalek
Azzi Abdelmalek 2013-6-9
Give a short example, and tell what should be the result?
lounis chehrit
lounis chehrit 2021-6-8
what about a signal which is for example:
Real(X(s))=34cos(2*pi*s/20) + 2cos(4*pi*s)
Imag(X(s))=21 sin(2*pi*s/3) + 20 sin(15*pi*s/12)
how can i find the transfer function? without the complex J.
And how can i compute the laplace inv without errors please ?

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回答（1 个）

Azzi Abdelmalek
Azzi Abdelmalek 2013-6-9
编辑：Azzi Abdelmalek 2013-6-9
If you have the transfer function G, you can get the numerator and denominator by using getdata function, then use this code
w=-10:0.1:10 % Frequency vector
N=[1 2] % Transfer function numerator
D=[1 3 2] % Transfer function Denominator
syms w
g=poly2sym(N,i*w)/poly2sym(D,i*w)
w=-10:0.1:10
h=double(subs(g))
plot(abs(h))
  3 个评论
显示 1更早的评论
Victor Manuel Chan Ortiz
Victor Manuel Chan Ortiz 2020-4-3
You can do:
g=poly2sym(N,s)/poly2sym(D,s);
g=subs(g,s,w*1i)
And replace w with the value that you need
lounis chehrit
lounis chehrit 2021-6-8
what about a signal which is for example:
Real(X(s))=34cos(2*pi*s/20) + 2cos(4*pi*s)
Imag(X(s))=21 sin(2*pi*s/3) + 20 sin(15*pi*s/12)
how can i find the transfer function? without the complex J.
And how can i compute the laplace inv without errors please ?

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