  An analytical method was developed to estimate errors in quantities depended
on full one-port vector network analyser (VNA) measurements using differentials
and a complex differential error region (DER) was defined. To evaluate the
method, differences instead of differentials were placed over a DER which was
then analysed and compared with another commonly used estimated error. Two real
differential error intervals (DEIs) were defined by the greatest lower and
least upper bounds of DER projections. To demonstrate the method, a typical
device under test (DUT) was built and tested against frequency. Practically, a
DER and its DEIs are solely based on manufacturer's data for standard loads and
their uncertainties, measured values and their inaccuracies.
