How to plot magnitude and phase spectrum of the function

Question

MUHAMMAD RAHMAT ASMAT 2020-6-16

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/549192-how-to-plot-magnitude-and-phase-spectrum-of-the-function

回答： Usman 2023-12-4

采纳的回答： Star Strider

Hye i really confuse on how much method to write the code to plot magnitude and phase. Below is my function.

X(z)=z / (z-1)^2

Any idea how to start beside plot?

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Answer 1

Star Strider 2020-6-16

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/549192-how-to-plot-magnitude-and-phase-spectrum-of-the-function#answer_451959

在 MATLAB Online 中打开

Try this:

z = tf('z');
X = z / (z-1)^2;
bode(X)

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MUHAMMAD RAHMAT ASMAT 2020-6-16

Thank you for the fast respond!

but sadly the first line give me this

>> z=tf('z');

Unrecognized function or variable 'tf'.

My code is actually like this:

>> Fs=11025;

>> nBits=16;

>> nChannels=1;

>> duration=5;

>> arObj=audiorecorder(Fs,nBits,nChannels);

>> fprintf('Press any key to start %g seconds of recording...',duration);pause

Press any key to start 5 seconds of recording...>>

>> fprintf('Recording...');

Recording...>>

>> recordblocking(arObj, duration);

>> fprintf('Finished recording.\n');

Finished recording.

>> fprintf('Press any key to play the recording...');pause;fprintf('\n');

Press any key to play the recording...

>> play(arObj);

>> audiosaved=getaudiodata(arObj);

>> audiowrite(‘C:\Users\User10\Desktop\Y3S2\DSP\projek\Code\recorder.wav’,audiosaved,Fs);

>> y=getaudiodata(arObj);

>> plot(y);

>> Fs=11025;

>> [p1,Fs]=audioread(‘C:\Users\User10\Desktop\Y3S2\DSP\projek\Code\recorder.wav’);

>> q=11025;

>> audioM=p1(ceil(1.47*q):floor(q*1.7),:);

>> audiowrite(‘C:\Users\User10\Desktop\Y3S2\DSP\projek\Code\audioM.wav’,audioM,Fs);

>> Plot(audioM);

>> load('g12_voicerecord_M.mat')

>> Fs=11025;

>> [p2,Fs]=audioread('C:\Users\User10\Desktop\Y3S2\DSP\projek\Code\audioM.wav');

>> plot(p2);

>> d=decimate(p2,500);

>> amp=10*d;

>> syms amp

>> f=amp;

>> ztrans(f)

ans =

z/(z - 1)^2

it is a audio that i manipulate to extract only one word and decimate it by 500 and amplify it by 10, after that i use z transform to get the last answer which is ans = z/(z - 1)^2 and from here i cannot do any plotting to magnitude and phase because i confuse which one to use.

Sorry for the long explanation, but i try to make it short.

MUHAMMAD RAHMAT ASMAT 2020-6-16

Hye sorry to bother again, but i just raelize that after i amplify the signal and try to z transform it, it give me the ans, but i think it was not correct. Maybe my code is not accurate or vise versa.

>> d=decimate(p2,500);

>> amp=10*d;

>> syms amp %from here i think my z transform it not valid

>> f=amp;

>> ztrans(f)

ans =

z/(z - 1)^2

i need to calculate the spectrum of the decimated signal using Z-transform technique

Star Strider 2020-6-16

I have no idea what you are doing, and I cannot run your code. I cannot imagine how you get a transfer function straight out of a decimated signal, or what ‘calculate the spectrum of the decimated signal using Z-transform technique’ refers to.

If you are estimating a transfer function from the input to and output of a discrete (sampled) system in either the time-domain or frequency-domain, you can either use the System Identification Toolbox functions (there are several that could apply), or the Signal Processing Toolbox invfreqz function. You will need to experiment with whatever functions you choose to use to get the result you want.

.

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