  The objective of the paper is to assess the accuracy of a standard FDTD code
in the analysis of the near and far-field characteristics of two-dimensional
models of small-size dielectric lens antennas made of low or high-index
materials and fed by the line sources. We consider extended hemielliptic lenses
and use the Muller boundary integral equations method as a suitable reference
solution. Inaccuracies of FDTD near so-called half-bowtie resonances are
detected. Denser meshing reduces the error of FDTD only to a certain level
determined by the type of absorbing boundary conditions used and other fine
details of the code. Out of these resonances, FDTD code is demonstrated as
capable of providing sufficient accuracy in the near and far-field analysis of
small-size hemielliptic lenses typical for the mm-wave applications.
