Conversions between VSWR - Return Loss - Reflection coefficient

A transmission line connected to a load

When a transmission line (a feeder cable, for example) is connected to a load (say an antenna) a reflection may occur if both impedances are not matched. This means that part of the energy may be reflected back towards the source instead of reaching the load. The superposition of waves traveling forward and backward on the same cable forms a standing wave.

There are several ways of quantifying this phenomenon, the most common are:


VSWR = Vmax/Vmin = (1+rho)/(1-rho)    ;     RL = -20 log10 (rho)    ;     rho = | (Zl - Zc) / (Zl + Zc) |

Voltage standing wave ratio: VSWR =  : 1 [1/1]
Return loss: RL = dB
Reflection coefficient: ρ = [1/1]
Line impedance: Zc =  + j 0 Ω
Load impedance: Zl =  + j  Ω

Enter the VSWR, the return loss, the reflection coefficient or the impedances. Than click the "Calculate" button next to the value you just typed to compute the two (or three) others. Unfortunately, an infinite combination of impedances gives the same VSWR and therefore is not possible to calculate the impedance starting from the other parameters.


Home Electronics Index Previous page Next page