How do I filter a signal, using FIR filters.
7 views (last 30 days)
Show older comments
Peter Cristian
on 26 Mar 2022
Edited: Scott MacKenzie
on 26 Mar 2022
I've got this code, what filter, and how should i use it to only show me in the end the component with the 300Hz frequency? Using a fir filter
```
t = 0:1/8000:1023/8000;
w = 0:8000/1024:4000;
x = 0.5*sin(2*pi*50*t) + 0.5*square(2*pi*130*t) + 0.3*sawtooth(2*pi*250*pi) + 0.2*sin(2*pi*300*t);
h =
y = filter(h,1,x);
figure;
subplot(2,1,1), plot(t,x);
z = abs(fft(x)) / 512;
subplot(2,1,2), plot(w, z(1:513));
figure;
subplot(2,1,1), plot(t,y);
z = abs(fft(y)) / 512;
subplot(2,1,2), plot(w, z(1:513));
```
0 Comments
Accepted Answer
Scott MacKenzie
on 26 Mar 2022
You could perhaps use a butterworth bandpass filter: (Note: Requires Signal Processing Toolbox)
t = 0:1/8000:1023/8000;
w = 0:8000/1024:4000;
x = 0.5*sin(2*pi*50*t) + 0.5*square(2*pi*130*t) + 0.3*sawtooth(2*pi*250*pi) + 0.2*sin(2*pi*300*t);
% h =
% y = filter(h,1,x);
% create bandpass butterworth filter @ 300 Hz
fCutoff1 = 250;
fCutoff2 = 350;
[b, a] = butter(6, [fCutoff1 fCutoff2]/(8000/2), 'bandpass');
% filter the signal
y = filter(b, a, x);
figure;
subplot(2,1,1), plot(t,x);
z = abs(fft(x)) / 512;
subplot(2,1,2), plot(w, z(1:513));
figure;
subplot(2,1,1), plot(t,y);
z = abs(fft(y)) / 512;
subplot(2,1,2), plot(w, z(1:513));
2 Comments
Scott MacKenzie
on 26 Mar 2022
Edited: Scott MacKenzie
on 26 Mar 2022
I just used order six as it seemed to do a reasonable job in excluding neighboring frequencies. At order 3, for example, you get this:

More Answers (0)
See Also
Categories
Find more on Filter Analysis in Help Center and File Exchange
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!