Phase difference removal by using Filtering, butterworth, filtfilt command

32 views (last 30 days)
Hi Guys!
I am using 6th order Butterworth bandpass filter to extract the 10-20 Hz band from the signal (x). After that, I applied the filtfilt command on to the Butterworth bandpass filtered signal (10-20 Hz) to remove the phase delay. Is that I am doing right?
Thanks in advance. The code is given below. Feel free to correct the code.
Fs = 500;
fcutlow = 6; % low cut frequency in Hz
fcuthigh = 14; % high cut frequency in Hz
[b,a] = butter(6,[fcutlow,fcuthigh]/(Fs/2));
Butterworth_bandpass_filter = filter(b,a,x);
Filt_filt_signal = filtfilt(b,a, Butterworth_bandpass_filter);

Accepted Answer

Alberto Mora
Alberto Mora on 5 Jun 2020
Edited: Alberto Mora on 5 Jun 2020
I think that you just need to do:
Fs = 500;
fcutlow = 6; % low cut frequency in Hz
fcuthigh = 14; % high cut frequency in Hz
[b,a] = butter(6,[fcutlow,fcuthigh]/(Fs/2));
Filt_filt_signal = filtfilt(b,a, rawSignal );
without "Butterworth_bandpass_filter = filter(b,a,x);", otherwise you firstly compute a filter on the signal (with phase lag), and then you pass the filtered signal into filtfilt routine that filter again twice the incoming signal, but the incoming signal is already with a phase delay.
If you wanto to be sure about the results, have a look the frequency domain, comparin initial and final spectrums.
  4 Comments
Nimish Iwale
Nimish Iwale on 8 Jul 2020
Is there any way this can be implemented in Simulink? I want to remove the phase shift in a simulink model.

Sign in to comment.

More Answers (0)

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!