Band Pass filter Design
It is designed by giving higher cut of frequency and lower cut of frequencies. We record EEG signal externally by using Electrodes. Because of that Skin noise, skull noise, disturbance noise, power line noise etc noise present in EEG signal. For removing the higher cut off and lower cut of frequency from the signal band pass filter is used. We want the signal frequency up to 30 Hz because the beta band frequencies is up to that frequency.
Design the Band pass Butterworth filter in the matlab by using the code
Design the Band pass Butterworth filter in the matlab by using the code
Algorithm:
i) First take eeg input data
ii) Pot that data
iii) Mention the sampling frequency
iv) Calculate the normalize frequency by using formula fnormal = cut of frequency (Fs/2)
v) Then design the butter of the filter in that we put the order of filter, normalize
frequency , curve type, for this we take two vectors.
vi) Then filter the data using Filtfilt . it performs zero-phase digital filtering by
processing the input data, x, in both the forward and reverse directions filtfilt operates along the first nonsingleton dimension of x. The vector b provides the
numerator coefficients of the filter and the vector a provides the denominator
coefficients. If you use an all-pole filter, enter 1 for b. If you use an all-zero filter (FIR), enter 1 for a. After filtering the data in the forward direction, filtfilt reverses
the filtered sequence and runs it back through the filter.
vii) Finally plot the original signal and filtered signal in the one plot
viii) Takes the fft of that filtered signal
ix) Plot that fft
x)Now that signal is filtered and its frequency is similar to we given as input cut of frequency of signal.
i) First take eeg input data
ii) Pot that data
iii) Mention the sampling frequency
iv) Calculate the normalize frequency by using formula fnormal = cut of frequency (Fs/2)
v) Then design the butter of the filter in that we put the order of filter, normalize
frequency , curve type, for this we take two vectors.
vi) Then filter the data using Filtfilt . it performs zero-phase digital filtering by
processing the input data, x, in both the forward and reverse directions filtfilt operates along the first nonsingleton dimension of x. The vector b provides the
numerator coefficients of the filter and the vector a provides the denominator
coefficients. If you use an all-pole filter, enter 1 for b. If you use an all-zero filter (FIR), enter 1 for a. After filtering the data in the forward direction, filtfilt reverses
the filtered sequence and runs it back through the filter.
vii) Finally plot the original signal and filtered signal in the one plot
viii) Takes the fft of that filtered signal
ix) Plot that fft
x)Now that signal is filtered and its frequency is similar to we given as input cut of frequency of signal.
Band pass filter is designed for filter EEG signal for specific frequency. Four filters are designed for the different frequency bands. The filtered signals for all frequency spectrum band, actual signal and fft of different frequency band is shown bellow.
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