characteristic admittance

File:TransmissionLineDefinitions.svg is drawn as two black wires. At a distance x into the line, there is current phasor I(x) traveling through each wire, and there is a voltage difference phasor V(x) between the wires (bottom voltage minus top voltage). If $Y\_0$ is the characteristic admittance of the line, then $I(x)\; /\; V(x)\; =\; Y\_0$ for a wave moving rightward, or $I(x)/V(x)\; =\; -Y\_0$ for a wave moving leftward.]]

Characteristic admittance is the mathematical inverse of the characteristic impedance.

The general expression for the characteristic admittance of a transmission line is as follows:

:$Y\_0=\backslash sqrt\{\backslash frac\{G+j\backslash omega\; C\}\{R+j\backslash omega\; L\}\}$

where

:$R$ is the resistance per unit length,

:$L$ is the inductance per unit length,

:$G$ is the conductance of the dielectric per unit length,

:$C$ is the capacitance per unit length,

:$j$ is the imaginary unit, and

:$\backslash omega$ is the angular frequency.

The current and voltage phasors on the line are related by the characteristic admittance as:

:$\backslash frac\{I^+\}\{V^+\}\; =\; Y\_0\; =\; -\backslash frac\{I^-\}\{V^-\}$

where the superscripts $+$ and $-$ represent forward- and backward-traveling waves, respectively.