 Standing wave ratio

On a uniform lossless transmission line, incident and reflected sinusoidal waves give voltage maxima $|V^{+}|(1+|\Gamma |)$ and minima $|V^{+}|(1-|\Gamma |)$. Their ratio is the voltage standing wave ratio, $(1+|\Gamma |)/(1-|\Gamma |)$, where $\Gamma$ is the voltage-wave reflection coefficient. A matched termination gives one, while perfect reflection gives an infinite ratio. These expressions assume a common real characteristic impedance and no propagation attenuation between the compared extrema.

The Standing Wave Ratio (SWR), often referred to as Voltage Standing Wave Ratio (VSWR), is a measure used in radio and telecommunications to quantify the efficiency of power transmission in a transmission line. It specifically indicates how well the load (such as an antenna) is matched to the transmission line. SWR is defined as the ratio of the maximum voltage (V_max) to the minimum voltage (V_min) along the transmission line.