An analytical method was developed, to estimate uncertainties in full two-port Vector Network Analyzer measurements, using total differentials of S-parameters. System error uncertainties were also estimated from total differentials involving two triples of standards, in the Direct Through connection case. Standard load uncertainties and measurement inaccuracies were represented by independent differentials. Complex uncertainty in any quantity, differentiably dependent on S-parameters, is estimated by the corresponding Differential Error Region. Real uncertainties, rectangular and polar, are estimated by the orthogonal parallelogram and annular sector circumscribed about the Differential Error Region, respectively. From the users point of view, manufactures data may be used to set the independent differentials and apply the method. Demonstration results include: (1) System error differentials for Short, matching Load and Open pairs of opposite sex standards; (2) System error uncertainties for VNA extended by two lengthy transmission lines of opposite sex end-connectors; (3) High uncertainties in Z-parameters against frequency of an appropriately designed, DC resistive, T-Network; (4) Moderate uncertainties in amplitude and phase patterns of a designed UHF radial discone antenna (azimuthally rotated by a built positioner, under developed software control of a built hardware controller) polarization coupled with a constructed gain standard antenna (stationary) into an anechoic chamber.
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