PRACTICAL MATLAB® FOR ENGINEERS PRACTICAL MATLAB

Analog and Digital Filters 641

Example 6.15

Create the script fi le multiban that returns the realization of a digital multiband nor-

malized fi lter with the specs indicated by the sketch shown in Figure 6.65, using the

following functions:

a. fi r2 of order 50, with a Bartlett window (FIR)

b. remez (FIR) of order 50

c. yulewalk digital IIR of order 15

MATLAB Solution

% Script File: multiban

w = [0 .1 .2 .3 .4 .5 .6 .7 .8 1];

mag = [0 0 1 1 0 0 1 1 0 0];

hnfir = fir2(50,w,mag,bartlett(51));

[h1, w1] = freqz(hnfir,1,256);

subplot (3,1,1)

plot (w1/pi, abs(h1))

ylabel (‘gain‘)

title (‘Multiban filter using fir2 (with bartlett window)’)

xlabel(‘frequency W (in rad)’)

subplot (3,1,2)

hnrem = remez(50,w,mag);

[h2, w2] = freqz (hnrem,1,256);

plot (w2/pi, abs(h2))

ylabel (‘gain‘)

title (‘Multiban filter using remez’)

xlabel(‘frequency W (in rad)’)

subplot(3,1,3)

[num,den] = yulewalk(15,w,mag);

[hiir,w] = freqz(num,den,256);

plot(w/(pi),abs(hiir))

ylabel (‘gain’)

title (‘Multiban filter using yulewalk’)

xlabel(‘frequency W (in rad)’)

The script fi le multiban is executed and the results are as follows (Figure 6.66):

>> multiban

FIGURE 6.65

Filter’s specs of Example 6.15.

H(W)

0

W (rad.)

1

.2 .4 .6 .8 1.0