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TF, DIRAC, CONVOLUTION, ET TUTTI QUANTI - ESIEE Paris

TF, DIRAC, CONVOLUTION, ET TUTTI QUANTI - ESIEE Paris

TF, DIRAC, CONVOLUTION, ET TUTTI QUANTI - ESIEE Paris

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Page 22 <strong>TF</strong>, Dirac, convolution, et tutti quanti<br />

• 2 e cas :<br />

-1/Te<br />

-1/Te<br />

|Xe(f)|<br />

1/Te 2/Te<br />

|Xe(f)|<br />

1/Te 2/Te<br />

1<br />

Te<br />

-fmax<br />

> 2fmax<br />

|Xe(f)|<br />

0<br />

Il n’y a pas de recouvrement de spectre, TeXe(f) et X(f) coïncident entre −1/2Te et 1/2Te.<br />

Pour reconstruire x(t) à partir de xe(t), il suffit alors de faire passer xe(t) dans un filtre passe-bas idéal de<br />

fonction de transfert H(f) :<br />

La sortie y(t) de ce filtre passe-bas vérifie :<br />

fmax<br />

<br />

f<br />

H(f) = Terect<br />

fe<br />

-1/2Te<br />

H(f)<br />

Te<br />

fe<br />

f<br />

1/2Te<br />

Y (f) = H(f)Xe(f) = X(f),<br />

1/Te<br />

f<br />

f<br />

f

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