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The Neper (Np) is similar to
the decibel (dB). It's unitless and is used to express ratios. The
Neper uses the natural logarithm, and is named after Microwave Hall-of-Famer
John Napier. Instead of using
the logarithm function (base 10), the Neper uses the base "e".
For voltage ratio of a/b, the difference in calculation is shown
The difference between a dB and
a Neper is just a fixed ratio. This is computed by dividing the
The simplification is done by
noting that ln(x)=log(x)*ln(10), if you remember your high-school
math. Nepers are typically used in loss calculations in the attenuation
constant of the propagation constant:
is in nepers/meter.
This is important, so remember
How about we immortalize the Neper conversion as Microwaves101 Rule of Thumb #119:
To convert Nepers to decibels, multiply by (approximately) 8.68.
dB/Np = 20/ln(10)=8.68588