  The accuracy of two equivalent antenna representations, near-field sources
and far-field sources, are evaluated for an antenna installed on a simplified
platform in a series of case studies using different configurations of
equivalent antenna representations. The accuracy is evaluated in terms of
installed far-fields and surface currents on the platform. The results show
large variations between configurations. The root-mean-square installed
far-field error is 4.4% for the most accurate equivalent representation. When
using far-field sources, the design parameters have a large influence of the
achieved accuracy. There is also a varying accuracy depending on the type of
numerical method used. Based on the results, some recommendations on the choice
of sub-domain for the equivalent antenna representation are given. In
industrial antenna applications, the accuracy in determining e.g. installed
far-fields and antenna isolation on large platforms are critical. Equivalent
representations can reduce the fine-detail complexity of antennas and thus give
an efficient numerical descriptions to be used in large-scale simulations. The
results in this paper can be used as a guideline by antenna designers or system
engineers when using equivalent sources.
