Using Butterworth Filter in Matlab

Answer 1

% program to design butterworth low pass filter

clc;

clear all;

close all;

alphap=input ('enter the pass band ripple');

alphas=input('enter the stop band ripple');

fp=input('enter the pass band freq');

fs=input('enter the stop band freq');

F=input('enter the sampling freq');

omp=2*fp/F;oms=2*fp/F;

%to find cut off freq and order of the filter

[n,wn]=buttord(omp,,oms,alphap,alphas);

% system function of the filter

[b,a]=butter(n,wn,'step');

w=0:0.01:pi;

[h,om]=freq(b,a,w);

m=2*log(abe(h));

an=angle(h);

subplot(2,1,1);

plot(om/pi,m);

ylabel('magnitude');

xlabel(''om/pi);

title('magnitude');

subplot(2,1,2);

plot(om/pi,an);

ylabel('phase angle');

xlabel('om/pi');

title('phase angle');