EE342.01: MATLAB M-FILE FOR PLOTTING A DISCRETE-TIME SIGNAL AND ITS DTFT

%
%  Filename:  example8.m
%
%  Description:  M-file to plot discrete-time signals and their DTFT.
%

n = 0:20;                         % define DT variable

xfast = (-0.95).^n;               % define DT signals
xslow = (0.95).^n;

subplot(2,2,1);                   % plot slow signal
stem(n,xslow);
grid;
xlabel('n');
ylabel('x[n] = (0.95)^n');
title('Slow Varying DT Signal');

subplot(2,2,3);                   % plot fast signal
stem(n,xfast);
grid;
xlabel('n');
ylabel('x[n] = (-0.95)^n');
title('Fast Varying DT Signal');

W = -3*pi:0.01:3*pi;		  % define DT frequencies

Xfast = 1./(1+(0.95)*exp(-j*W));   % define DTFT of signals
Xslow = 1./(1-(0.95)*exp(-j*W));   

subplot(2,2,2);                   % plot DTFT of slow signal
plot(W,abs(Xslow));
grid;
xlabel('Discrete Frequency');
ylabel('|DTFT[(.95)^n]|');
title('Magnitude Spectrum of Slow Signal');

subplot(2,2,4);                   % plot DTFT of fast signal
plot(W,abs(Xfast));
grid;
xlabel('Discrete Frequency');
ylabel('|DTFT[(-.95)^n]|');
title('Magnitude Spectrum of Fast Signal');