Sampled signal spectrum ?

someone knows the matlab program to plot a the spectrum of a sampled signal ; example : signal x(t) ?

Answer 1

[Suraj Kumar]

Hi Nabil,

To plot the spectrum of a sampled signal in MATLAB, we can use the Fast Fourier Transform (FFT) to convert the time-domain signal into its frequency-domain representation.To learn more about 'fft' function in MATLAB, please refer to the following documentation link: https://www.mathworks.com/help/matlab/ref/fft.html

We can compute the two-sided spectrum and convert it to a single-sided spectrum to get the amplitude of the frequency components. We can define the frequency domain (`f`) for plotting and then visualize the single-sided amplitude spectrum. This will allow us to see the dominant frequencies present in the signal.

You can refer to the attached code snippet for better understanding:

Fs = 400;            
T = 1/Fs;             
L = 1000;              
t = (0:L-1)*T;         
f1 = 100;               
f2 = 200;              
x = 0.5+ cos(2*pi*f1*t) + 2*cos(2*pi*f2*t);  
 
figure;
plot(t, x);
title('Time-Domain Signal');
xlabel('Time (s)');
ylabel('Amplitude');

 
X = fft(x); 
P2 = abs(X/L); 
P1 = P2(1:L/2+1);
P1(2:end-1) = 2*P1(2:end-1);
 
f = Fs*(0:(L/2))/L; 
figure;
plot(f, P1);
title('Single-Sided Amplitude Spectrum of x(t)');
xlabel('Frequency (Hz)');
ylabel('|P1(f)|');

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Happy Coding!