PRACTICAL MATLAB® FOR ENGINEERS PRACTICAL MATLAB

Time Domain Representation of Continuous and Discrete Signals 53

MATLAB Solution

% Script file: signal _ noise

n = 1:128; P =2.7;

figure(1)

subplot(2,1,1)

white _ noise = sqrt(P)*randn(1,128);

stem(n,white _ noise); hold on;plot(n,white _ noise);

xlabel(‘discrete time n’);

ylabel(‘Amplitude’); title(‘Gaussian noise’);

subplot(2,1,2)

signal = cos(2*pi*n/64);

stem(n,signal);hold on;plot(n,signal);

title(‘cosine wave with period=64’)

xlabel(‘discrete time n’);

ylabel(‘Amplitude’);

figure(2)

signal _ noise = white _ noise+signal;

stem(n,signal _ noise);hold on;plot(n,signal _ noise);

title(‘cosine wave plus white Gaussian noise’)

xlabel(‘discrete time n’);

ylabel(‘Amplitude’);

The script fi le signal_noise is executed as follows and the results are shown in

Figures 1.43 and 1.44.

FIGURE 1.43

Plots of parts a and b of R.1.161.

Gaussian noise

4

2

0

− 2

− 4

0 20 40 60 80 100 120 140

Amplitude

Amplitude

discrete time n

cosine wave with period = 64

1

0.5

0

−0.5

− 1

(^020406080100120140)
discrete time n