Image:Signal bruit et fourier.png
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[edit] Summary
Spectre (transformée de Fourier) d'un signal bruité
Spectrum (Fourier transform) of a signal with noise
Auteur/author : Christophe Dang Ngoc Chan (cdang)
Réalisé avec/made with Scilab
clear;clf;
// ******************
// variable ajustable
p=0.1; // pas
// ******************
// variables de base
x=[0:p:20*%pi]'; // x du sinus
N=size(x);
n=N(1,1); // nombre de points
s=1/p*(1:n); // fréquences
// nombres aleatoires, loi uniforme
y2=0.2*(rand(n,1)-0.5);
// ******************
// Calcul
y1=sin(x);
y3=y1+y2;
z1=abs(fft(y1))^2;
z2=abs(fft(y2))^2;
z3=abs(fft(y3))^2;
for i=1:n
if z1(i)>500 then z1(i)=500; end
if z3(i)>500 then z3(i)=500; end
end
// ******************
// affichage
subplot(3,2,1)
plot2d(x,y1,style=2,rect=[0,-1.1,60,1.1])
xtitle('signal sinusoïdal','Temps','Intensité')
subplot(3,2,2)
plot2d(s,z1,style=2,rect=[0,0,0.03,50])
xtitle('TF signal sinusoïdal','Fréq.','Puissance')
subplot(3,2,3)
plot2d(x,y2,style=2,rect=[0,-1.1,60,1.1])
xtitle('bruit','Temps','Intensité')
subplot(3,2,4)
plot2d(s,z2,style=2,rect=[0,0,0.03,50])
xtitle('TF bruit','Fréq.','Puissance')
subplot(3,2,5)
plot2d(x,y3,style=2,rect=[0,-1.1,60,1.1])
xtitle('signal sinusoïdal bruité','Temps','Intensité')
subplot(3,2,6)
plot2d(s,z3,style=2,rect=[0,0,0.03,50])
xtitle('TF signal sinusoïdal bruité','Fréq.','Puissance')
[edit] Licensing
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