PRACTICAL MATLAB® FOR ENGINEERS PRACTICAL MATLAB

524 Practical MATLAB® Applications for Engineers

0 0.5

−1.5

− 1

−0.5

0

0.5

Amplitude

1

1.5

2

1 1.5 2

Time

2.5 3 3.5

× 10 −^3

4

[noise+0.3*sin(2*pi*1000*t)+0.93*cos(2*pi*200*t)+0.69*sin(2*pi*3000*t)] versus t

Communication signal = information + noise

FIGURE 5.37
Plot of signal(t) = noise + f(t) of Example 5.8.

signal _ n = noise+0.7*sin(2*pi*1000*t)+0.93*cos(2*pi*2000*t)+0.69*sin

(2*pi*3000*t);

figure(1)

plot (t(1:33),signal _ n(1:33))

title(‘[noise+0.3*sin(2*pi*1000*t)+0.93*cos(2*pi*2000*t)+0.69*sin(2*pi*

3000*t)] vs t’)

xlabel(‘time’); ylabel(‘Amplitude’);

figure(2)

DFT _ mag = abs(fft(signal _ n,256));

DFT _ phase = angle(fft(signal _ n,256));

subplot (2,1,1)

DFTX = DFT _ mag(1:1:128);

W = [1:1:N/2].*fs/N;

plot (W,DFTX); title(‘DFT Magnitude and Phase’)

ylabel (‘Magnitude’);xlabel(‘frequency in Hertz’)

subplot (2,1,2)

DFTY= DFT _ phase(1:1:128);

W = [1:1:N/2].*fs/N;

plot (W,DFTY);xlabel(‘frequency in Hertz’); ylabel (‘Angle’)

The script fi le signal_n is executed and the results are indicated in the Figures 5.37

and 5.38.