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.

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.

Answer 1

[Alberto]

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

[Sam]

thanks.. exactly what i wanted...