Calculating Return-Loss Uncertainty

For reflection measurements, the uncertainty in magnitude VRC, U(|*|) can be converted to the equivalent return loss uncertainty, U(RL), using Eq. 3⁸:

where:
* = the measured VRC.
Calculating phase uncertainty:
For a given S-parameter, Sij (i = 1, 2; j = 1, 2), the uncertainty in phase, U(*), can be estimated using Eq. 4⁹:

where:
U(|Sij|) = the uncertainty in |Sij|.
When calculating the uncertainty in transmission phase, it is first necessary to determine the uncertainty in the magnitude of the linear transmission coefficient (i.e. U(|S21|) or U(|S12|)). This can be derived from the measured attenuation, A, and the uncertainty in the measured attenuation, U(A), using Eq. 5⁸: