Applying the transmission line model based on the telegrapher equations, the general expression for the characteristic impedance of a transmission line is: The telegraphers equations (or just telegraph equations) are a pair of linear differential equations which describe the voltage and current on an electrical transmission line with distance and time. ...
The voltage and current phasors on the line are related by the characteristic impedance as: Electrical resistance is a measure of the degree to which an electrical component opposes the passage of current. ... Inductance (or electric inductance) is a measure of the amount of magnetic flux produced for a given electric current. ... Electrical conductance is the reciprocal of electrical resistance. ... Capacitance is a measure of the amount of electric charge stored (or separated) for a given electric potential. ... See wikibooks book on Phasors A phasor is a constant complex number representing the complex amplitude (magnitude and phase) of a sinusoidal function of time. ...
where the superscripts + and − represent forward- and backward-traveling waves, respectively.
Lossless line
For a lossless line R and G are zero and the equation for characteristic impedance reduces to
A transmission line is the material medium or structure that forms all or part of a path from one place to another for directing the transmission of energy, such as electromagnetic waves or acoustic waves, as well as electric power transmission. ... Maxwells equations (sometimes called the Maxwell equations) are the set of four equations, attributed to James Clerk Maxwell, that describe the behavior of both the electric and magnetic fields, as well as their interactions with matter. ...
The acoustic impedance Z (or sound impedance) is the ratio of sound pressure p to particle velocity v in a medium or acoustic component.
The characteristicimpedance of a medium (usually air, but also for instance exhaust gases in a muffler) is the ratio of sound pressure p to particle velocity v in open field (i.e.
The acoustic impedance Z of an acoustic component (in Pa·s/m) is the ratio of sound pressure p to particle velocity v at a transition with a previous component:
Characteristicimpedance is determined by the size and spacing of the conductors and the type of dielectric used between them.
For ordinary coaxial cable used at reasonable frequency, the characteristicimpedance depends on the dimensions of the inner and outer conductors, and on the characteristics of the dielectric material between the inner and outer conductors.
In a nut shell the characteristicimpedance of a coax cable is the square root of (the per unit length inductance divide by the per unit length capacitance).
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