How to make bode plot of transfer function

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Hello, i am trying to make a bode plot of the transfer function of a twin-t notch filter, that i am analyzing. I was able to produce the transfer function, and the bode plot by hand, but i am struggling to do it in Matlab, here is what i have so far:
r=320; %Resistance
c=100*10^-9; %Capactiance
p=(1/(r.*c)); %Beta
a=0.95; %Signma, adjusts the wiper of a potentiometer
f=(5000); %Target Frequency
s= (1i*f);
h=((s^2 + p^2) ./ (s^2+4*p*s*(1-a)+p^2)); %Transfer function
mh=abs(h); %Magitude of h
ah=angle(h); %Phase angle of h, in rads.
I am trying to plot the body function, and here is one i made for the transfer function H=2/(s+1):
% Example Transfer Function: g(s) = 2/(s+1)
% Numerator num = [2]; % Denominator den = [1 1];
% Transfer Function G = tf(num, den)
% Plot Frequency Response bode(G), grid
My question is, how would i represent the numerator and the denominator, since they are both powers of of s, which from my understanding the computer understands as s=jw, and thus i solved the transfer function as such. I have tried to understand how exactly the bode function takes it inputs, but i am not understanding that...
Any help would be great!!!
Thanks, Mike
  1 Comment
Mike Zylla
Mike Zylla on 15 Apr 2016
here is the actual example code:
% Numerator
num = [2];
% Denominator
den = [1 1];
% Transfer Function
G = tf(num, den)
% Plot Frequency Response
bode(G), grid

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Accepted Answer

Star Strider
Star Strider on 15 Apr 2016
Your transfer function would use:
num = [1 0 p^2];
den = [1 4*p*(1-a) p^2];
I’m certain you can take it from there.
Also, remember that the bode function can output the results of its computations, and the bodeplot function allows you to tweak its behaviour.
  6 Comments
Prasad Adavi
Prasad Adavi on 19 Oct 2022
r=320; %Resistance
c=100*10^-9; %Capactiance
p=(1/(r.*c)); %Beta
a=0.95; %Signma, adjusts the wiper of a potentiometer
f=(5000); %Target Frequency
s= (1i*f);
%h=((s^2 + p^2) ./ (s^2+4*p*s*(1-a)+p^2)); %Transfer function
num = [1 0 p^2];
den = [1 4*p*(1-a) p^2];
h=tf(num,den)
bode(h), grid
Star Strider
Star Strider on 19 Oct 2022
Easier —
r=320; %Resistance
c=100*10^-9; %Capactiance
p=(1/(r.*c)); %Beta
a=0.95; %Signma, adjusts the wiper of a potentiometer
f=(5000); %Target Frequency
% s= (1i*f);
s = tf('s');
h=((s^2 + p^2) / (s^2+4*p*s*(1-a)+p^2)); %Transfer function
% num = [1 0 p^2];
% den = [1 4*p*(1-a) p^2];
% h=tf(num,den)
bode(h), grid
.

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More Answers (1)

Irshad Baruah
Irshad Baruah on 6 Sep 2019
how to implement bode plot for transfer function=s^a

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