  In order to demonstrate the usefulness of the only one existing method for
systematic error estimations in VNA (Vector Network Analyzer) measurements by
using complex DERs (Differential Error Regions), we compare one-port VNA
measurements after the two well-known calibration techniques: the quick
reflection response, that uses only a single S (Short circuit) standard, and
the time-consuming full one-port, that uses a triple of SLO standards (Short
circuit, matching Load, Open circuit). For both calibration techniques, the
comparison concerns: (a) a 3D geometric representation of the difference
between VNA readings and measurements, and (b) a number of presentation figures
for the DERs and their polar DEIs (Differential Error Intervals) of the
reflection coefficient, as well as, the DERs and their rectangular DEIs of the
corresponding input impedance. In this paper, we present the application of
this method to an AUT (Antenna Under Test) selected to highlight the existence
of practical cases in which the time consuming calibration technique results a
systematic error estimation stripe including almost all of that of quick
calibration.
