having a problem using an iir notch filter
19 次查看(过去 30 天)
显示 更早的评论
hello everyone,
i want to filter 50 Hz sinus and therefore i implemented a notch filter such as shown in the help. i don'w know why it doesn't work. does everyone have a clue ? see also the attached file 'debuging' this is the program :
if true
% code
end
*t=0:0.0005:0.5; % fs=2000Hz
x=sin(2*pi*50*t)+sin(2*pi*70*t);
figure;
plot(t,x);
title('Sum of sinuses - of 50Hz & of 70Hz ');
% implementation of the notch filter
wo = 50/(2000/2); bw = wo/35;
[b,a] = iirnotch(wo,bw);
fvtool(b,a);
%signal after filterization
figure;
g=filter(b,a,x);
plot(t,g);
title('The signal after removing its 50 Hz sinus');
%figure of 70 Hz for comarison to what i need to get
figure;
y=sin(2*pi*70*t);
plot(t,y);
title('A 70 Hz sinus - for comparison');*
thanks a lot
0 个评论
采纳的回答
Wayne King
2014-1-5
Kobi, did you also supply the optional Ab input argument as I did?
nyquist = 2000/2;
w0 = 50/nyquist;
bw = w0/20;
[b,a] = iirnotch(w0,bw,20);
y = filtfilt(b,a,x);
plot(t,y);
From your output it does not appear that you did.
If you execute the above, you should see that is pretty much a clean 70-Hz sinewave with a reduction in amplitude.
0 个评论
更多回答(3 个)
Wayne King
2014-1-4
It is working, you just need to tweak the parameters a bit to get better results.
nyquist = 2000/2;
w0 = 50/nyquist;
bw = w0/20;
[b,a] = iirnotch(w0,bw,20);
y = filter(b,a,x);
ydft = fft(y);
plot(abs(ydft))
0 个评论
另请参阅
类别
在 Help Center 和 File Exchange 中查找有关 Digital Filter Analysis 的更多信息
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!