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Characteristic Impedance




The SI unit of characteristic impedance is the Ohm .


DESCRIPTION


A uniform line terminated in its characteristic impedance will have no Standing Wave s, no reflections from the end, and a constant ratio of voltage to current at a given Frequency at every point on the line. The characteristic impedance of a linear, homogeneous, Isotropic , Dielectric Propagation Medium free of electric charge is given by the relation

:Z_0 = \sqrt{\mu \over \epsilon} = {1 \over {c \ \epsilon}} = c \mu

where

:Z_0 \ is the characteristic impedance
:\epsilon \ is the electric Permittivity of the medium (in Farads per meter)
:\mu \ is the magnetic Permeability of the Medium (in Henries per meter)
:c = rac{1}{\sqrt{ \mu \epsilon}} \ is the speed of propagation in the medium

When the medium is Free Space , the magnetic permeability \mu_0 \ and electric permittivity \epsilon_0 \ of free space are used and this defines the universal Physical Constant , the characteristic impedance of free space:

:Z_0 = \sqrt{\mu_0 \over \epsilon_0} = {1 \over {c \ \epsilon_0}} = c \mu_0 = 376.73 \ \Omega

where

:c = {1 \over \sqrt{ \mu_0 \epsilon_0}} \ = 2.998 imes 10^8 \ \mbox{m/s} is the Speed Of Light in free space,

:\epsilon_0 = 8.854 imes 10^{-12} \ \mbox{F/m} is the Permittivity Of Free Space , and

:\mu_0 = 4 \pi imes 10^{-7} \ \mbox{H/m} is the Permeability Of Free Space .


SEE ALSO



SOURCE

Adapted from