MATLAB CODE TO DESIGN A CHEBYSHEV II BAND REJECT FILTER

CODE:

clear all

alphap=2;  %passband attenuation in dB

alphas=20; %stopband attenuation in dB

wp=[.1*pi,.5*pi]; % passband freq. in radians

ws=[.2*pi,.4*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,'STOP')

w=0:.01:pi;

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

m=20*log(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 =  3

wn =0.2000    0.4000

b =0.8622   -3.0407    5.9953   -7.2774    5.9953   -3.0407    0.8622

a =1.0000   -3.3568    6.2813   -7.2539    5.6903   -2.7480    0.7433