# matlab and transfer function

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#### franticEB

##### Full Member level 3
Hi i need to obtain this transfer function with matlab
$H(s)=\frac{0.7560*s^3}{(s^2+0.5704*s+1)*(s^2+0.4216*s+2.9224)*(s^2+0.1443*s+0.3422)}$

where the frequency parameter s is normalized with respect to ωn = 130,590 s–1.
It defines a sixth-order bandpass filter with a 1-dB equiripple passband in 12 kHz ≤ f ≤ 36 kHz.

Anyone could help me please? How can i use filter function of matlab (i.e ellip,cheby,butter) to obtain H(s)?

#### opopson

##### Member level 1
Matlab has inbuilt filter functions just type help and then type the name of the filter you want to use. Then query! But if you want to use your own fitler function create an m-file for it, you may need to declare s as a symbol.

#### nitishn5

##### Full Member level 5
If you want only this exact transfer function. You can use the function 'tf'.

H = tf([0.7650 0 0 0], [1 0.5704 1]) * tf([1], [1 0.4216 2.9224]) * tf([1], [1 0.1443 0.3422])

Or you can use the "filter design and analysis toolbox", 'fdatool' to make general filters.

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