Bande passante

En téléphonie, la norme CCITT prévoit une bande passante de 3100Hz comprise entre 300Hz et 3400Hz.

Bande passante idéale: caractère de Nyquist

B ≤ Ds ≤ 2B

Nous pouvons aussi dire que :

(Ds/2) ≤ B ≤ Ds

  • B = Bande passante 3100Hz
    (300Hz -> 3400Hz = 80% de degré de justesse).
  • Ds = 1/Δ
  • Δ = plus petit instant significatif

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L'intervalle de Nyquist est l'intervale entre deux échantillons d'un même signal :

i = 1 / (2 . fmax)

  • i = intervale.
  • fmax = fréquence maximum.
    En téléphonie, nous pouvons donc dire que l'intervale de Nyquist correspond à 1 / (2 . 4 KHz) = 1/8000 Hz = 125 µs

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Document created the 14/07/2003, last modified the 26/10/2018
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