This calculator estimates the gain uncertainty (or gain ripple) caused by reflections in an RF chain. It takes into account the return losses of the source, input, output and load, as well as the gain and reverse isolation of the amplifier.
It is particularly useful for RF and microwave engineers to evaluate gain stability in amplifiers, filters and transmission networks subject to impedance mismatches.
Formulas
P = 10^((-RLs – RLi) / 20) + 10^((G – RLl – RLs – ISO) / 20) + 10^((-RLo – RLl) / 20)
Gmin = 20 × log10(1 – P)
Gmax = 20 × log10(1 + P)
Explanation of formulas
- RLs, RLi, RLo and RLl represent the return losses of the source, input, output and load.
- G corresponds to the gain of the amplifier in dB, and ISO to its inverse isolation.
- The P parameter evaluates the combined effect of reflections in the system.
- The Gmin and Gmax values determine the uncertainty range of the total gain in dB.
Example of gain uncertainty calculation for a 20 dB amplifier
Input : RLs = 20 dB, RLi = 15 dB, RLo = 18 dB, RLl = 15 dB, G = 20 dB, ISO = 30 dB
Output : Gmin ≈ 19.87 dB, Gmax ≈ 20.12 dB
Benefits and uses
- Used to evaluate gain stability in RF circuits.
- Helps identify mismatch effects between components.
- Useful in the design of amplifiers and measurement chains.
- Improves the accuracy of RF performance models.