Need help to write a program to plot a magnitude response and phase response of a signal x (n) = a^n*u(n) .a) using loop b) using MATLAB command for DFT.

Question

Sam 2014-9-3

1
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https://ww2.mathworks.cn/matlabcentral/answers/153290-need-help-to-write-a-program-to-plot-a-magnitude-response-and-phase-response-of-a-signal-x-n-a-n

评论： Sam 2014-9-26

采纳的回答： Alberto

Hi all,

Please suggest a code for a program to plot a magnitude response and phase response of a signal x (n) = a^n*u(n).

a) using loop b) using MATLAB command for DFT.

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Answer 1

Alberto 2014-9-5

1
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https://ww2.mathworks.cn/matlabcentral/answers/153290-need-help-to-write-a-program-to-plot-a-magnitude-response-and-phase-response-of-a-signal-x-n-a-n#answer_150875

在 MATLAB Online 中打开

DFT is:

so you can make it by using loop or matlab FFT function directly, hope this help:

%%using loop
%a is a constant
clear
a=2;
N=100;
for k=1:N
    X(k)=0;
    for n=1:N  %this include u(n)
        x(n)=a.^n; 
        X(k)= X(k)+(x(n)*exp(-j*2*pi*(k-1)*(n-1)/N));
    end
end
subplot(2,1,1),plot(abs(X))  %magnitude
subplot(2,1,2),plot(angle(X)) %phase
%%using FFT
%a is a constant
clear
a=2;
N=100;
n=[1:1:N];
x=a.^n;
X=fftshift(fft(x),N);
subplot(2,1,1),plot(n,abs(X))  %magnitude
subplot(2,1,2),plot(n,angle(X)) %phase