PRACTICAL MATLAB® FOR ENGINEERS PRACTICAL MATLAB

624 Practical MATLAB® Applications for Engineers

phase3=angle(h3);

subplot(1,3,3);

plot(w,phase3);axis([0 3 -2 2]);

xlabel(‘freq w(rad/sec)’);

ylabel(‘phase in rad’);

title(‘Chebyshev 2, phase plot’)

Back in the command window, the script fi le butt_chev is executed and the magnitude

and phase plots are shown in Figures 6.51 and 6.52.

FIGURE 6.51
Magnitude plots of the analog LP Butterworth, Chebyshev/type-1, and Chebyshev/type-2 fi lters of Example 6.6.

20

Butterworth LPF, N 
 5

10

 10

 20

 30

 40

 50

 60

 70

 80

05

frequency w (rad/s)

0

gain, db

05

frequency w (rad/s)

20

Chebyshev 1 LPF, N 
 5

 20

 40

 60

 80

 100

0

gain, db

01 2

frequency w (rad/s)

Chebyshev 2 LPF, N 
 5

10

 10

 20

 30

 40

 50

0

gain, db

FIGURE 6.52
Phase plots of the analog LP Butterworth, Chebyshev/type-1, and Chebyshev/type-2 fi lters of Example 6.6.

Butterworth, phase plot

4

3

2

1

phase in rad

0

 1

 2

 3

 4

0231

freq w (rad/s)

Chebyshev 1, phase plot

4

3

2

1

phase in rad

0

 1

 2

 3

 4

012

freq w (rad/s)

Chebyshev 2, phase plot

2

1.5

1

0.5

0

 1

 2

phase in rad

0312

freq w (rad/s)

0.5

1.5