600
Practical MATLAB
® Applications for Engineers
g. Repeat ͉H(f)͉ versus f
∠H(w) versus f
͉H(f)͉ dB versus f (semilog scale)
∠H(f ) versus f (semilog scale)
using standard circuit techniques.
ANALYTICAL Solution
Part (a)
H w
V w
V w
jwC
jwC
R
R C
j w
R C
o
i
( )
( )
( )
*
*
*
ϭ
ϭ
ϩ
ϭ
ϩ
1
1
1
1
Part (b)
H w
R C
w
R C
( ) ϭ
ϩ
1
1
2
2
*
*

 

 
∠H(w) = tan
−1 (w * R * C)
MATLAB Solution
% Script File: LP _ filter _ analysis
R=1e3/(2*pi);
C=.1e-6;
a=1/(R*C);
w =-5*a:10000:5*a;
num=a;
den=[1 a];
Hlp = freqs(num,den,w);
figure(1);
subplot(2,1,1);
plot(w/(2*pi),abs(Hlp));
xlabel (‘frequency in Hrz’);
ylabel (‘magnitude’);
title(‘Magnitude of H(f) vs. frequency’);
FIGURE 6.25
Circuit diagram of Example 6.1.
R = 1/(2 * π) KΩ
C = 1 µF
V i (w )
V o (w )
CRC_47760_CH006.indd 600
CRC_47760_CH006.indd 600
7/23/2008 2:26:42 PM
7/23/2008 2:26:42 PM