retake

Code.m

@@ -0,0 +1,8 @@
+signal = csvread('unknownsignal.csv');
+Fs = 650; %Hz
+
+frequencySpectrum(signal,Fs);
+
+figure;
+title('Spectrogram of Unknown Signal')
+spectrogram(signal,[],[],[],Fs,'yaxis');

frequencySpectrum.m

@@ -0,0 +1,48 @@
+function power = frequencySpectrum(signal, fs)
+%%%%%%%%%%%%%%%%%%
+%function frequencySpectrum(signal, fs)
+%
+% Task: Display the power spectrum of a given signal
+%
+% Input:
+%	- signal: the input signal to process
+%	- fs: the sampling rate
+%
+% Output: 
+%	- power: power spectrum of the signal
+%	
+%
+% Guillaume Gibert, guillaume.gibert@ecam.fr
+% 25/04/2022
+%%%%%%%%%%%%%%%%%%
+
+n = length(signal);          % number of samples
+
+y = fft(signal, n);% compute DFT of input signal
+power = abs(y).^2/n;    % power of the DFT
+
+[val, ind] = max(power); % find the mx value of DFT and its index
+
+% plots
+figure;
+
+subplot(1,3,1) % time plot 
+t=0:1/fs:(n-1)/fs; % time range
+plot(t, signal)
+xticks(0:0.1*fs:n*fs);
+xticklabels(0:0.1:n/fs);
+xlabel('Time (s)');
+ylabel('Amplitude (a.u.)');
+
+subplot(1,3,2) % linear frequency plot
+f = (0:n-1)*(fs/n);     % frequency range
+plot(f,power, 'b*'); hold on;
+plot(f,power, 'r');
+xlabel('Frequency (Hz)')
+ylabel('Power (a.u.)')
+
+subplot(1,3,3) % log frequency plot
+plot(f,10*log10(power/power(ind)));
+xlabel('Frequency (Hz)')
+ylabel('Power (dB)')
+