Standing Wave Ratio
Definition
A measure of how much of a wave reflects back at a boundary — 1:1 means perfect transmission, higher means more reflection.
Symbol: · Unit: dimensionless (ratio)
Technical definition
SWR = maximum amplitude / minimum amplitude along the line. SWR = 1 indicates no reflection (perfect impedance match); higher values indicate greater reflected power. Critical in radio antenna and transmission-line design.
Example
A radio antenna with SWR 1.5:1 is well matched — most power radiates. An SWR of 5:1 means serious mismatch, with much power reflected back toward the transmitter.
SWR measures the standing wave pattern caused by reflection — it does not directly tell you the reflected power fraction (that is the reflection coefficient). SWR 2:1 does not mean half the power reflects.