86 Practical MATLAB® Applications for Engineers
Example 1.18
An analog communication system consists of an information signal or message given
by m(t) = 3 cos(5t), and a high-frequency carrier given by fc(t) = cos(50t).
- Create the script fi le modulation that returns the following plots:
a. m(t) versus t
b. fc(t) versus t
c. Amplitude modulated (AM) signal versus t
d. Angle modulated (FM/PM) signal versus t - Let us assume now that the message signal m(t) is a binary-periodic signal with
period T = 2 , defi ned as follows:
mt
t
t
()
30 1
11 2
Obtain the plots of the following communication signals:
a. ASK versus t
b. FSK versus t
c. PSK versus t
f(n) versus n
5
− 5
0
0
Amplitude
Amplitude
Amplitude
10 20 30 40 50 60 70 80 90 100
5
− 5
0
f(n) is resampled with L=3/M=2
f(n) is resampled with L=2/M=3
0 50 100 150
time index n
time index n
5
0
010 2030405060
time index n
− 5
FIGURE 1.72
Plots of f(t) and resampled f(t) with notes given by L/M of Example 1.17.