MATLAB CODE TO DESIGN A CHEBYSHEV II LOWPASS FILTER

CODE:

clear all

alphap=1;  %passband attenuation in dB

alphas=20; %stopband attenuation in dB

wp=.2*pi; % passband freq. in radians

ws=.3*pi; % stopband freq. in radians

%to find cutoff freq. and order of the filter

[n,wn]=cheb2ord(wp/pi,ws/pi,alphap,alphas) %syatem function of the filter

[b,a]=cheby2(n,alphap,wn)

w=0:.01:pi;

[h,ph]=freqz(b,a,w);

m=abs(h);

an=angle(h);

subplot(2,1,1);plot(ph/pi,m);grid;

ylabel('Gain in dB');

Xlabel('NORMALISED FREQUENCY')

subplot(2,1,2);plot(ph/pi,an);grid

ylabel('phase in radians');

xlabel('noramlised frequency')

 OUTPUT:

n =4

wn =0.3000

b =0.7164   -0.3652    1.0067   -0.3652    0.7164

a =1.0000   -0.6698    1.1096   -0.2540    0.5234