A transmission line is drawn as two black wires. At a distance x into the line, there is current phasorI(x) traveling through each wire, and there is a voltage difference phasor V(x) between the wires (bottom voltage minus top voltage). If is the characteristic admittance of the line, then for a wave moving rightward, or 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: