PRACTICAL MATLAB® FOR ENGINEERS PRACTICAL MATLAB

638 Practical MATLAB® Applications for Engineers

aa = a(1:7)’;

[nn aa]

disp(‘*********************’)

m = 0:1:mid;

w = -pi:.01*pi:pi;

subplot(2,2,1)

stem(n,h)

axis([0 15 -6 5])

xlabel(‘time index n’)

ylabel(‘Amplitude ‘)

title(‘[Impulse sequence h(n)] vs. n’)

subplot(2,2,2)

stem(0:mid,a)

xlabel(‘ index n’)

ylabel(‘Amplitude’)

title(‘[coeff. a1(n)] vs. n’)

H1 = a(1)+a(2)*cos(w)+a(3)*cos(2*w)+a(4)*cos(3*w)+a(5)*cos(4*w);

H2 = a(6)*cos(5*w)+a(7)*cos(6*w);

H = H1+H2;

subplot(2,2,3)

plot(w,H)

xlabel(‘W‘);ylabel(‘Amplitude’)

title(‘H1(W) vs. W’)

subplot(2,2,4)

zplane(h,1)

title(‘zero-pole plot’)

The script fi le Fir_typ1_1 is executed and the results are shown as follows:

>> Fir _ typ1 _ 1

****coeff. of H1(w)****

index n coeff. a(n)

ans =

0 3

1 -2

2 4

3 8

4 6

5 4

6 -10

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

Example 6.14

Create the script fi le fi lter_wind that returns the normalized LP-FIR fi lters using the

command fi r1 in conjunction with the following windows:

a. Kaiser (β = 3.5)

b. Hanning

c. Blackman

d. Hamming

e. Tr i a ng u l a r

f. Bartlett

The fi lter’s specs are N = 64 and Rp = 1.4 dB.