Dear colleagues
I would like to perform a FFT low pass filtration on my 100000 point data in MATLAB? How can i do that?
what do you mean by FFT low filter?
you want to apply low filter in frequency domain?
what does it means by low pass filtration and what type of point data you work on ?
Dear Friends
I mean i need to perform a Fast Fourier Transform (FFT) low pass filtering on a time domain data. I have a data file containing of 100000 data point by 0.01 time interval.
Simply convolve your data by a window(hamming or Hanning or Gaussian window).
why you want to use FFT?
if you want to use FFT then follow the instruction mentioned below:
1-divide your data into some overlapped windows.
2-take FFTof each window. remove the frequencies low than f_0(the low pass filter frequency).
3-Take IFFT of each window.
Dear Hossein
Is it necessary to divide my data into some windows? why the whole data can not be used?
Hi Sayyed,
I suggest you have a look at the following Matlab functions:
[b,a] = butter(n,Wn,ftype) This will design a Butterworth filter with the characteristics that you need. A Butterworth filter is designed to have as flat as possible a response in pass band. If you need different characteristics, other functions are avaialable to design different kinds of filters.
y = filtfilt(b,a,x) Once you have your b and a from the previous step, then you can use these to filter your signal x.
Let me know if you have further questions.
Costanzo
Follow the suggestion by Costanzo Di Maria and implement the digital filter directly. If you use filtfilt, as he suggests it avoids issues of phase and delay.
I would suggest you may use FIR1 filter. Which can be implemented using FDAtool in MATLAB very easily. If you still not able to Figure out let me know I can share my code for filtering.
Dear Vijayakumar
May you provide me your code please. it would be very appreciated for this issue.
Hi
check below link,
cheers
http://www.cs.uregina.ca/Links/class-info/425/Lab5/
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