| a unit used to express the ratio of two field quantities by the natural logarithm of this ratio
NOTE 1 – The value of a power ratio in nepers is one half the natural logarithm of this power ratio. The values in nepers of the ratio of two field quantities and of the two corresponding powers are equal only if the impedances are equal.
NOTE 2 – Sub-multiples such as the decineper are also used with the symbol dNp.
NOTE 3 – One neper equals 8.686 dB.
NOTE 4 – In some disciplines the neper may be used to express the logarithm of a power ratio without the factor 1/2. An example is attenuation also called optical depth in radiometry. Such usage is deprecated in telecommunications, in order to avoid ambiguity; in this case one neper would be equal to 4.343 dB.