Standing wave ratio
![Incident wave (blue) is fully reflected (red wave) out of phase at short-circuited end of transmission line creating a net voltage (black) standing wave. Γ=-1, SWR=∞.](/Images/godic/202502/13/Standing_wave_24659.gif")
![Standing waves on transmission line, net voltage shown in different colors during one period of oscillation. Incoming wave from left (amplitude = 1) is partially reflected with (top to bottom) Γ= .6, -.333, and .8∠60°. Resulting SWR = 4, 2, 9.](/Images/godic/202502/13/StandingWaves-34659.png")
In radio engineering and telecommunications, standing wave ratio (SWR) is a measure of impedance matching of loads to the characteristic impedance of a transmission line or waveguide. Impedance mismatches result in standing waves along the transmission line, and SWR is defined as the ratio of the partial standing wave's amplitude at an antinode (maximum) to the amplitude at a node (minimum) along the line.