First compute reflection coefficient magnitude from VSWR, then calculate −20 log10 of that magnitude. The result is positive return loss for an ordinary passive mismatch.
How it works in practice
VSWR near 1 gives a small reflection coefficient and large return loss. Precision near an excellent match can be limited by measurement uncertainty. An ideal VSWR of exactly 1 implies zero reflection and mathematically infinite return loss; real measurements have finite resolution.
Example and interpretation
VSWR 1.2 gives a magnitude near 0.0909 and return loss about 20.83 dB.
Checks before use
- Calculate reflection magnitude
- Apply the return-loss formula
- Round within measurement capability
- State frequency
Important limit
Do not report mathematically infinite matching quality from a rounded display of 1.00.
Related Centron RF product
SMA 2 W 6 GHz fixed attenuator. Use calculated levels to define a requirement, then compare it with the exact product’s current bandwidth, input power, impedance and available attenuation options. Calculations assume stated conditions and do not replace a component datasheet.
Further reading
Keysight: Fundamentals of RF and Microwave Power Measurements. This background reference explains general principles; the selected Centron RF model’s datasheet governs its own ratings.
Related guides
Educational guide. Numerical examples use the stated assumptions and are not test results for a supplied unit.