630 Practical MATLAB® Applications for Engineers
Example 6.9
Create the script fi le cheby_HPF that returns the coeffi cients of the digital transfer func-
tion and the magnitude and phase plots of a third-order Chebyshev type-1 and -2 digi-
tal HPFs with the following specs:
- wc = 0.5 rad/s
- T = 0.3
- Rp = 2 dB
- Rs = 3 dB
MATLAB Solution
% Script file: cheby _ HPF
N =3; % order
Rp = 2; Rs = 3; % ripples
T = .3; % sampling period
Wc = .5; % cut off frequency
Wz = -2pi:.01pi:3pi;
wzc = WcT/pi; % normalized dig. frequency
[Pz1, Qz1] = cheby1(N, Rp, wzc, ‘high’);
disp(‘****’)
disp(‘*R E S U L T S *****’)
disp(‘****’)
disp(‘For the transfer function H(z) of the Cheby/type1 HPF’)
disp(‘the numerators coefficients are:’)
disp(Pz1)
disp(‘The denominator coefficients are:’)
disp(Qz1)
[Pz2, Qz2] = cheby2(N, Rs, wzc, ‘high’);
disp(‘ For the transfer function H(z) of the Cheby/type2 HPF’)
disp(‘The numerators coefficients are:’)
FIGURE 6.58
Magnitude and phase plots of H(z) of Example 6.8.
− (^505)
0.4
0.5
0.6
0.7
0.8
0.9
1
1.1
Mag.of digital LPF
magnitude
− 2 − 1 0 1 2
− 30
− 20
− 10
0
10
20
30
Phase of digital LPF versus w
W in rad W in rad
phase in degrees