PRACTICAL MATLAB® FOR ENGINEERS PRACTICAL MATLAB

646 Practical MATLAB® Applications for Engineers

The Butterworth LPF satisfying the given specs is shown in Figure 6.71.

% frequency plots for the network of Figure 6.71

L01=15e-3;L02=5e-3; C0=1.33e-6;

num=1;

den=[L01*L02 L01*C0 L01+L02 1];w = -155000: 250 : 155000;

hnn = freqs(num,den,w);

gain = 20 * log10 (abs (hnn));

f = w./(2 * pi);

subplot (2,1,1)

plot (f, gain)

ylabel (‘Gain in db’)

title (‘Magnitude of [H(f)] vs. f’)

subplot (2,1,2)

plot ( f,angle(hnn).*180/ pi)

xlabel (‘ f in Hertz ’)

ylabel ( ‘ Angle in degrees’)

title (‘ Phase of [H(f)] vs. f ’);

Example 6.18

Create the script fi le IIR-yul that returns the magnitude and phase plots of IIR nor-

malized LP digital fi lter of orders 4, 6, 8, and 10 using the function yulewalk with the

magnitude–frequency specs given by the following MATLAB vectors:

f = [0:0.1:1.0]

mag = [1 1 1 .707 0 0 0 0 0 0 0]

FIGURE 6.70
Elements of normalized LPF of Example 6.17.

1.5 H

1.33 F

0.5 H

1 Ω

Vi(s) Vo(s)

L 1

C

L 2

R

FIGURE 6.71
Scaled elements of the Butterworth LPF of Example 6.17.

15 mH

1.33 μF

5 mH

100 Ω

Vi(s) Vo(s)

L 1

C 0

L 2

R 0