  A local permittivity model is proposed to accurately characterize spatial
dispersion in non-local wire-medium (WM) structures with arbitrary
terminations. A closed-form expression for the local thickness-dependent
permittivity is derived for a general case of a bounded WM with lumped
impedance insertions and terminated with impedance surfaces, which takes into
account the effects of spatial dispersion and loads/terminations in the
averaged sense per length of the wire medium. The proposed approach results in
a local model formalism and accurately predicts the response of WM structures
for near-field and far-field excitation. It is also shown that a traditional
transmission network and circuit model can be effectively used to quantify the
interaction of propagating and evanescent waves with WM structures. In
addition, the derived analytical expression for the local thickness-dependent
permittivity has been used in the full-wave numerical solver (CST Microwave
Studio) demonstrating a drastic reduction in the computation time and memory in
the solution of near-field and far-field problems involving wire media.
