create a firfilter

firFilter.m

@@ -0,0 +1,37 @@
+function signal_filtered = firFilter(N, cutoffFreq, signal, samplingFreq)
+%{
+function signal_filtered = firFilter(N, cutoffFreq, signal, samplingFreq)
+Ex: signal_filtered = firFilter(30, [5 20], x, 200)
+
+Task: Apply an FIR bandpass filter to a signal.
+
+Inputs:
+    - N: filter order
+    - cutoffFreq: 2-element vector [low high] for bandpass cutoff (Hz)
+    - signal: input signal to be filtered
+    - samplingFreq: sampling frequency (Hz)
+
+Output:
+    - signal_filtered: the filtered output signal
+
+Author: Tikea TE
+Date: 16/04/2025
+%}
+
+% Normalize the cutoff frequency
+Wn = cutoffFreq / (samplingFreq / 2);  % Normalize to Nyquist
+
+% Design the FIR bandpass filter using Hamming window
+b = fir1(N, Wn, 'bandpass', hamming(N+1));
+a = 1;  % FIR filter has only numerator
+
+% Apply filter
+signal_filtered = filter(b, a, signal);
+
+% Plot frequency response
+figure;
+freqz(b, a, 1024, samplingFreq);
+title('Frequency Response of FIR Filter');
+grid on;
+
+end

iirFilter.m

@@ -1,60 +1,39 @@
-function [signal_filtered, Z, P] = iirFilter(N, cutoffFreq, signal, samplingFreq, filterType)
+function [signal_filtered, Z,P] = iirFilter(N, cutoffFreq, signal, samplingFreq, filterType)
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-% function [signal_filtered, Z, P] = iirFilter(N, cutoffFreq, signal, samplingFreq, filterType)
+% function [Z, P] = iirFilter(N, cutoffFreq, signal, samplingFreq, filterType)
-% ex.: [signal_filtered, Z, P] = iirFilter(6, [5 20], x, 200, 1)
+% ex.: [Z, P] =iirFilter(6, 10, x, 500, 1)
 %
-% Task:
+% Task: To create and analyze an IIR low pass filter (Butterworth ror Chebychev)
-%   To create and apply an IIR filter (Butterworth or Chebyshev)
-%   Supports low-pass or band-pass depending on the cutoffFreq input.
 %
 % Inputs:
-%   -N: order of the filter
+%	-N: order of the filter
-%   -cutoffFreq: scalar (for low-pass) or 2-element vector [low high] for bandpass
+%	-cutoffFreq: below this frequency, signal is not modified and above signal is attenuated
-%   -signal: input signal to be filtered
+%	-samplingFreq: sampling frequency (In Hz)
-%   -samplingFreq: sampling frequency in Hz
+%   -signal: signal to be filter    
-%   -filterType: 1 = Butterworth, 2 = Chebyshev type I
+%	-filterType: Butterworth if equal to 1 and Chebychev if equal to 2
 %
 % Outputs: 
-%   -signal_filtered: filtered signal
-%   -Z: filter zeros
-%   -P: filter poles
 %	
-% Author: Tikea TE
+%
-% Date: 16/04/2025
+% Author: Guillaume Gibert, guillaume.gibert@ecam.fr
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+% Date: 09/04/2025
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 
-% Design the filter
+if (filterType == 1)
-if filterType == 1
+	[b, a] = butter(N, cutoffFreq/(samplingFreq/2));
-    if length(cutoffFreq) == 1
+elseif (filterType == 2)
-        [b, a] = butter(N, cutoffFreq / (samplingFreq / 2), 'low');
+	Rp = 10; % bandpass ripple of Rp dB
-    elseif length(cutoffFreq) == 2
+	[b, a] = cheby1(N, Rp, cutoffFreq/(samplingFreq/2));
-        [b, a] = butter(N, cutoffFreq / (samplingFreq / 2), 'bandpass');
-    else
-        error('cutoffFreq must be scalar or 2-element vector');
-    end
-elseif filterType == 2
-    Rp = 10; % ripple for Chebyshev filter
-    if length(cutoffFreq) == 1
-        [b, a] = cheby1(N, Rp, cutoffFreq / (samplingFreq / 2), 'low');
-    elseif length(cutoffFreq) == 2
-        [b, a] = cheby1(N, Rp, cutoffFreq / (samplingFreq / 2), 'bandpass');
-    else
-        error('cutoffFreq must be scalar or 2-element vector');
-    end
 else
-    error('Filter type must be 1 (Butterworth) or 2 (Chebyshev)');
+	disp('Filter type is incorrect!')
+	return
 end
 
-% Analyze zeros/poles
 [Z, P] = zeroPole(a, b, 1);
 
-% Show frequency response
 figure;
 freqz(b, a, N, samplingFreq);
 title('Frequency response');
 grid on;
 
-% Apply filter to signal
 signal_filtered = filter(b, a, signal);
-
-end

main.m

@@ -23,8 +23,7 @@ plotRawSignal(X, Fs);
 [f, power] = frequencySpectrum(X, Fs, 1);  % set 1 to plot
 
 % ======== Apply a bandpass filter ==============
-[filteredSignal, Z, P] = iirFilter(6, [5 20], X, 200, 1);  % Butterworth bandpass
+[filteredSignal, Z, P] = iirFilter(10, [5 20], X, Fs, 1);
-
+plotFilteredSignal(filteredSignal, Fs);
-
 
 end