How I can plot the magnitude and phase response of the transfer function

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Mohsen Salimy 2019-12-26

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https://ww2.mathworks.cn/matlabcentral/answers/498096-how-i-can-plot-the-magnitude-and-phase-response-of-the-transfer-function

评论： Star Strider 2019-12-26

采纳的回答： Star Strider

Screenshot 2019-12-26 at 12.30.22.png

can someone help me figure this out. Screenshot 2019-12-26 at 12.30.22.png

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Answer 1

Star Strider 2019-12-26

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/498096-how-i-can-plot-the-magnitude-and-phase-response-of-the-transfer-function#answer_407795

在 MATLAB Online 中打开

Try this:

z = tf('z',-1);
H = tf((0.0534*(1+z^-1)*(1-10166*z^-1 + z^-2))/((1-0.683*z^-1)*(1-1.4461*z^-1+0.7957*z^-2)))
H.Variable = 'z^-1'
bode(H)

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Star Strider 2019-12-26

在 MATLAB Online 中打开

I assumed that you have the Control System Toolbox, and you want to use it to produce a Bode plot of your transfer function.

To create a Bode plot from the numerator and denominator coefficients:

z = tf('z',-1);
H = tf((0.0534*(1+z^-1)*(1-10166*z^-1 + z^-2))/((1-0.683*z^-1)*(1-1.4461*z^-1+0.7957*z^-2)))
H.Variable = 'z^-1'
num_zinv = H.Numerator{:}
den_zinv = H.Denominator{:}
figure
freqz(num_zinv, den_zinv, 2^14)                         % Filter Transfer Function: ‘z^-1’ Convention
%numerator coefficients 
b0 = 0.05634;
b1 = [1  1];
b2 = [1 -1.0166 1];
 %denominator coefficients
a1 = [1 -0.683];
a2 = [1 -1.4461 0.7957];
num = b0 * conv(b1,b2);
den = conv(a1,a2);
figure
freqz(num, den, 2^14)

Using the ‘z^-1’ representation (provided by the Control System Toolbox conversion):

num_zinv = 1.0e+02 * [0.000534000000000  -5.428110000000000  -5.428110000000000   0.000534000000000];
den_zinv = [1.000000000000000  -2.129100000000000   1.783386300000000  -0.543463100000000];

See the documentation on the freqz function to understand how to get outputs from it. The Signal Processing Toolbox does not (to my knowledge) have the ability to use ‘z^-1’ representation, so I used those provided by the Control System Toolbox.

Mohsen Salimy 2019-12-26