MATLAB: Best Filter Band design

butterbuttordhomework not originally tagged as homeworkSignal Processing Toolbox

Making of passband Filter. What is the best design?

Best Answer

The easiest way to do everything you want is to use the Signal Processing Toolbox designfilt function.

Use the freqz function to be certain the filter you designed is stable, and that it does what you want it to.

Use the filtfilt function to do the actual filtering. It has a maximally flat phase response, so will not introduce any phase distortion into your filtered signal.

Related Solutions

MATLAB: How to design FIR lowpass filter with cutoff frequency, fc1 = 20 Hz and FIR bandpass filter with cutoff frequency fc2 = 10 Hz and fc3 = 35 Hz.

Déjà vu

how to design IIR highpass filter with cutoff frequency of 20Hz and FIR bandpass filter with cutoff frequency of 10Hz and 15Hz?

Make the appropriate changes to get the cascaded filter you want.

MATLAB: Filter design parameter: radian/sec or 1/sec

The passbands and stopbands for the Signal Processing Toolbox filter functions are actually normalised to the closed interval [0, pi] radians. It is calculated as the passband and stopband frequency in Hz divided by the Nyquist frequency.

Example for frequency calculations for the filters your signal:

Ts = 0.002;                                             % Sampling Interval (seconds)
Fs = 1/Ts;                                              % Sampling Frequency (Hz)

Fn = Fs/2;                                              % Nyquist Frequency

Note that the highest frequency you can design in your filter is the Nyquist frequency, here 250 Hz.

An example of a Chebyshev Type II filter design for filtering an EKG signal is here:

Fs = 250;                                               % Sampling Frequency (Hz)
Fn = Fs/2;                                              % Nyquist Frequency (Hz)
Wp = [1.0   100]/Fn;                                    % Passband Frequencies (Normalised)
Ws = [0.5   101]/Fn;                                    % Stopband Frequencies (Normalised)
Rp = 10;                                                % Passband Ripple (dB)
Rs = 50;                                                % Stopband Ripple (dB)
[n,Ws] = cheb2ord(Wp,Ws,Rp,Rs);                         % Filter Order
[z,p,k] = cheby2(n,Rs,Ws);                              % Filter Design
[sosbp,gbp] = zp2sos(z,p,k);                            % Convert To Second-Order-Section For Stability
figure(3)
freqz(sosbp, 2^17, Fs)
EKG_filt = filtfilt(sosbp, gbp, EKG_original);          % Filter EKG Signal

The filter passband goes from 1 Hz to 100 Hz.

Best Answer

Related Solutions

MATLAB: How to design FIR lowpass filter with cutoff frequency, fc1 = 20 Hz and FIR bandpass filter with cutoff frequency fc2 = 10 Hz and fc3 = 35 Hz.

MATLAB: Filter design parameter: radian/sec or 1/sec

Related Question