PRACTICAL MATLAB® FOR ENGINEERS PRACTICAL MATLAB

414 Practical MATLAB® Applications for Engineers

FIGURE 4.61
Time and frequency plots of the signals of the block box system of Example 4.11.

20

− 20

− 5

− 2

1

5

0

0

− 5

5

0

02

510

time

(^15) − 40
− 10
− 20
− 2
4
1
0.5
0
0.5
−0.5
h(t) versus t
y(t) versus t
x(t) versus t X(w) versus w
0
0
2
0
5
20 40
− 40 − 20
− 20
0
0
20
0
0
60
40
20
20
40
Phase
− 2
0
2
Phase
phase
phase
frequency w (in rad/sec)
Magnitude & phase of Y(w)
Magnitude & phase of H(w)
magnitude
magnitude
Amplitude
Amplitude
Amplitude
Magnitude
Magnitude
Magnitude
xlabel(‘time’),title(‘ y(t) vs. t’);
ylabel(‘Amplitude’)
yw = magHw.*xw;
axis([5 15 -5 5])
subplot(3,2,6),plotyy(w,yw,w,phase);
xlabel(‘frequency w (in rad/sec)’), title(‘Magnitude & phase of Y(w)’);
The script fi le analysis is executed and the results are as follows (Figure 4.61):
TIME DOMAIN FREQUENCY DOMAIN

Example 4.12
Given the circuit shown in Figure 4.62,

1. Determine by hand the system transfer function H(s) = V 0 (s)/ Vi(s)


2. Obtain an expression for v 0 (t), from part 1, where vi(t) = u(t)


3. Use MATLAB to obtain plots of v 0 (t) versus t, using an analytical and symbolic
   approach