How to apply a bandstop filter after performing FFT
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How to apply a bandstop filter after performing FFT on the this data, to remove the spikes ? SC is the data matrix.
rows1 =length(SC(:,2));
incr1=1/(rows1+1)*12;
fmax1=12*(1-1/(rows1+1));
X1=[0:incr1:fmax1/2]';
Y1 = abs(fft(SC(1:rows1,2),rows1));
5 Comments
Walter Roberson
on 17 Jun 2021
Example:
data = randn(1, 50);
plot(data)
title('original data');
Y1 = fft(data);
bins_of_interest = 5:22;
damping = exp(-(1:length(bins_of_interest)));
Y1(bins_of_interest) = Y1(bins_of_interest) .* damping;
Y1(end+2-bins_of_interest) = conj(Y1(bins_of_interest));
back_data = ifft(Y1);
whos back_data
plot(back_data)
title('reconstructed')
Your bins_of_interest should be chosen according to the sampling frequency and the number of points, and which frequencies you want to filter out; one of the links I posted shows how "wide" each bin is. Your "damping" could be constant or could be any curve that is appropriate for your circumstances, in recognition that you might not be wanting to filter each frequency equally.
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