Infinite Impulse Response Filters - Introduction to Digital Signal Processing and Filter Design - page 237

a = denominator coefficients ( columns1-9 ) :

1 . 0000 − 6 . 2955 18 . 6910 − 33 . 6739 40 . 0927 − 32 . 2433 17 . 1366

− 5 . 5267 0 . 8406

Example 4.14

%MATLAB script to design a Chebyshev II highpass filter
%with Wp=0.5,Ws=0.4,Rp=0.5 and Rs=60
[N,Wn]=cheb2ord(0.5,0.4,0.5,60)
[b,a]=cheby2(N,60,Wn,'high');
[h,w]=freqz(b,a,256);
H=abs(h);
HdB=20*log10(H);
plot(w/pi,H);grid
title('Magnitude response of a Chebyshev II Highpass Filter')
ylabel('Magnitude')
xlabel('Normalized frequency')
%end

The magnitude response of this filter is of order 11, is shown in Figures 4.27
and 4.28.

Magnitude response of a Chebyshev II highpass filter

1

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1

0

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Normalized frequency

Figure 4.27 Magnitude response of a Chebyshev II highpass filter.