MATLAB CODE TO DESIGN A CHEBYSHEV I LOWPASS FILTER

CODE:

clear all

alphap=1;  %passband attenuation in dB

alphas=15; %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]=cheb1ord(wp/pi,ws/pi,alphap,alphas); %syatem function of the filter

[b,a]=cheby1(n,alphap,wn);

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 =4

wn =0.2000

b =0.0018    0.0073    0.0110    0.0073    0.0018

a =1.0000   -3.0543    3.8290   -2.2925    0.5507