Telecom Dictionary - Definitions of terms

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Neper (Np) - Definition and Use

Neper (Np) - A neper is a unit used to express ratios, such as gain, loss, and relative values. Note 1: The neper is analogous to the decibel, except that the Naperian base 2.718281828. . . is used in computing the ratio in nepers. Note 2: The value in nepers, Np , is given by Np = ln( x 1 / x 2 ), where x 1 and x 2 are the values of interest, and ln is the natural logarithm, i.e., logarithm to the base e. Note 3: One neper (Np) = 8.686 dB, where 8.686 = 20/(ln 10). Note 4: The neper is often used to express voltage and current ratios, whereas the decibel is usually used to express power ratios. Note 5: Like the dB, the Np is a dimensionless unit. Note 6: The ITU recognizes both units.