PRACTICAL MATLAB® FOR ENGINEERS PRACTICAL MATLAB

Analog and Digital Filters 621

title(‘Phase of H(w) vs. w’)

figure(2);bode(num,den);

title(‘Bode plots:magnitude and phase’)

figure(3);zplane(num,den);grid on;

title(‘zero-pole plot’)

disp(‘*********************************’);

disp(‘***** Numerical evaluations *****’);

disp(‘*********************************’);

disp(‘The system zero is at :’);roots(num)

disp(‘The system pole is at : ‘);roots(den)

disp(‘*********************************’);

Back in the command window, the script fi le active_fi lter is executed and the results are

shown as follows (Figures 6.48 through 6.50):

>> active _ filter

*********************************

****** Numerical evaluations *******

*********************************

The system zero is at :

ans =

-20

The system pole is at :

ans =

-3.3333e+003

*********************************

FIGURE 6.48

Magnitude and phase plots of H(w) of Example 6.5.

40

30

50

0

1,000 2,000 3,000 4,000 5,000

Magnitude of H (w) versus w

6,000 7,000 8,000 9,000 10,000

1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000 10,000

w in rad /sec

Magnitude

20

10

60

40

20

80

0

Angle in degrees w in rad /sec

Phase of H (w) versus w