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
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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