RF Characteristic Impedance

Physics | Electromagnetic | Characteristic impedance,  or surge impedance,  of a uniform transmission line, usually written `Z_0`, is the ratio of the amplitudes of voltage and current of a single wave propagating along the line; that is, a wave traveling in one direction in the absence of reflections in the other direction.

Characteristic impedance is determined by the geometry and materials of the transmission line and, for a uniform line, is not dependent on its length. The SI unit of characteristic impedance is the ohm.