Standing wave ratio

In telecommunication, standing wave ratio ( SWR ) is the ratio of the amplitude of a standing wave at an anti-node[?] (minimum) to the amplitude at an adjacent node (maximum).

Note 1: The standing wave ratio (SWR ) in a uniform transmission line[?] is given by where ρ is the reflection coefficient.

Note 2: Reflections occur as a result of discontinuities, such as an imperfection in an otherwise uniform transmission line, or when a transmission line is terminated with other than its characteristic impedance.

Source: from Federal Standard 1037C and from MIL-STD-188