Return Loss is a measure of the amount of energy that is reflected back at a discontinuity in a Radio Frequency Circuit . It is specified in dB.
This calculator converts Return loss (RL) to Voltage Standing Wave Ratio (VSWR).
VSWR = (1 + 10-RL/20)/(1 – 10-RL/20)
A Return Loss of 10 dB is equivalent to a VSWR of 1.93.
Note that like Return Loss, VSWR has no units. It is often written as a ratio relative to 1. For example, VSWR = 1.93:1
What is Return Loss?
Return loss is the ratio between the incident and reflected energy at the input of an RF system. Mathematically it is represented as
Return Loss = Incident Power / Reflected Power
In a good design, no power is reflected back. However in actual practice, there’s always some power that is returned back to the source on account of impedance mismatch.
A good design goal is to aim for a return loss of at least 14 dB across the specified frequency range. In general return loss should be as high as possible.
 Return Loss