# Characteristic Impedance of Transmission Line

The region through which a plane wave (unguided wave) travels is characterised by the

*intrinsic**impedance*(*Î·*) of the medium defined by the ratio of the electric field to the magnetic field. The guiding structure over which the transmission line wave (guided wave) travels is characterised the*characteristic impedance*(*Z*_{0}) of the transmission line defined by the ratio of voltage to current.Characteristic impedance of a transmission line is defined as the ratio of positively travelling voltage wave to current wave at any point on the line.

# Lossless Transmission Line

A transmission line is said to be lossless if

- the conductors of the line are perfect, i.e., the conductors have infinite conductivity and zero resistance (
*Ïƒ*= âˆž, R = 0), and - the dielectric medium between the conductors is ideal, i.e., the medium has zero conductivity and infinite resistance (
*Ïƒ*= 0, G = 0).

# Distortionless Transmission Line-Waveform Distortion

When the received signal is not identical with the transmitted signal, the signal is said to be distorted. There are two types of waveform distortion:*Frequency Distortion**Î±*. It is known that*Î±*is a function of frequency.*Phase Distortion*