band pass filter a signal using FFT
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I have a random signal containing frequencies from 1Hz to 1000Hz (as viewed on a spectrogram).
I want to extract the signal containing freqs from 200Hz to 600Hz from it and zero out other frequencies (band pass filter). How can I do it in freq. domain efficiently? (since my signal is very long, doing it in time domain is time consuming using filter coefficient method)
Please help with an example.
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Wayne King
2012-4-16
With such a high sampling frequency and that many samples, why don't you downsample the signal using decimate()?
Since you are only interested in content between 100 and 300 Hz, you can downsample that signal a lot - by at least a factor of 25.
y = decimate(input,25);
That will give you data sampled at 2 kHz and make designing your filter much, much easier.
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Wayne King
2012-4-16
Have you considered fftfilt()?
You can design your FIR filter using fdesign.bandpass and then use fftfilt().
Wayne King
2012-4-16
d = fdesign.bandpass('Fst1,Fp1,Fp2,Fst2,Ast1,Ap,Ast2',75,100,150,175,50,0.5,50,1e3);
Hd = design(d);
y = filter(Hd,x);
If you want an IIR filter
Hd1 = design(d,'butter');
y1 = filter(Hd1,x);
plot(psd(spectrum.periodogram,y1,'Fs',1e3,'NFFT',length(y1)));
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Joydeb Saha
2021-6-19
How to remove the spikes from the data with a narrow bandpass filter? How to apply an inverse FFT algorithm to recreate the time-series data (filtered) from the frequency domain to the time domain? attaching the data.
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