Return loss in dB is −20 log10 of reflection coefficient magnitude. Larger positive return loss means a smaller reflected fraction.
How it works in practice
The reflected power fraction equals 10 raised to −return loss/10. Distinguish return loss from S11 displayed as a negative dB magnitude; they can describe the same reflection with different signs. Verify the instrument convention.
Example and interpretation
20 dB return loss corresponds to 1% reflected power; 10 dB return loss corresponds to 10%.
Checks before use
- Identify the sign convention
- Calculate the power fraction
- Convert to percent
- Check the operating frequency
Important limit
Do not interpret a more negative S11 trace as worse matching without checking the convention.
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.