Filter a signal using fft | MATLAB | DSP

%Code to extract the 5 Hz signal:

clc

clear all

close all

x1=5;

x2=15;

x3=30;

t=0:0.001:2;

y1=sin(2*pi*t*x1);

figure;

plot(t,y1,'k');

title('Signal with 5 Hz');

y2=0.5*sin(2*pi*t*x2);

figure;

plot(t,y2,'g');

title('Signal with 15 Hz');

y3=0.3*sin(2*pi*t*x3);

figure;

plot(t,y3,'m');

title('Signal with 30 Hz');

x=y1+y2+y3;

figure;

plot(t,x,'c');

title('Added signal');

g=abs(fft(y1));

figure;

stem((g));

title('Magnitude response of 5 Hz signal');

g=abs(fft(y2));

figure;

stem((g));

title('Magnitude response of 15 Hz signal');

g=abs(fft(y3));

figure;

stem((g));

title('Magnitude response of 30 Hz signal');

gg=(fft(x));

figure;

g=abs(gg);

stem(g);

title('Magnitude response of composite signal');

i=find(g<900);

gg(i)=zeros(size(i));

figure;

m=ifft(gg);

plot(t,m,'b');

title('Filtered signal');

%Code to extract the 30 Hz signal:

clc

clear all

close all

x1=5;

x2=15;

x3=30;

t=0:0.001:2;

y1=sin(2*pi*t*x1);

figure;

plot(t,y1,'k');

title('Signal with 5 Hz');

y2=0.5*sin(2*pi*t*x2);

figure;

plot(t,y2,'g');

title('Signal with 15 Hz');

y3=0.3*sin(2*pi*t*x3);

figure;

plot(t,y3,'m');

title('Signal with 30 Hz');

x=y1+y2+y3;

figure;

plot(t,x,'c');

title('Added signal');

g=abs(fft(y1));

figure;

stem((g));

title('Magnitude response of 5 Hz signal');

g=abs(fft(y2));

figure;

stem((g));

title('Magnitude response of 15 Hz signal');

g=abs(fft(y3));

figure;

stem((g));

title('Magnitude response of 30 Hz signal');

gg=(fft(x));

figure;

g=abs(gg);

stem(g);

title('Magnitude response of composite signal');

i=find(g>310);

gg(i)=zeros(size(i));

figure;

m=ifft(gg);

plot(t,m,'b');

title('Filtered signal');

%Code to extract the 15 Hz signal:

clc

clear all

close all

x1=5;

x2=15;

x3=30;

t=0:0.001:2;

y1=sin(2*pi*t*x1);

figure;

plot(t,y1,'k');

title('Signal with 5 Hz');

y2=0.5*sin(2*pi*t*x2);

figure;

plot(t,y2,'g');

title('Signal with 15 Hz');

y3=0.3*sin(2*pi*t*x3);

figure;

plot(t,y3,'m');

title('Signal with 30 Hz');

x=y1+y2+y3;

figure;

plot(t,x,'c');

title('Added signal');

g=abs(fft(y1));

figure;

stem((g));

title('Magnitude response of 5 Hz signal');

g=abs(fft(y2));

figure;

stem((g));

title('Magnitude response of 15 Hz signal');

g=abs(fft(y3));

figure;

stem((g));

title('Magnitude response of 30 Hz signal');

gg=(fft(x));

figure;

g=abs(gg);

stem(g);

title('Magnitude response of composite signal');

i=find(g<450);

gg(i)=zeros(size(i));

i=find(g>550);

gg(i)=zeros(size(i));

figure;

m=ifft(gg);

plot(t,m,'b');

title('Filtered signal');