Metallic posts in a radial waveguide

The calculation of input impedance of Dielectric-Filled Edge-Slot (DFES) antennas [1] requires the knowledge of the effects of passive metallic posts in a radial waveguide. The present paper describes a method to determine the equivalent circuit parameters for a number of
z
-directed passive metallic posts, uniformly distributed along
\rho = l_{1}
, within an
E
-type radial waveguide, extending from
\rho = \delta_{0}
to
\rho = \infty
and whose axis is oriented along the
z
-axis. The waveguide is excited at its center by a
z
-directed coaxial stub of radius
\rho = \delta_{0}
, the waveguide dimension (d) in the
z
-direction is sufficiently small so that only the dominant mode fields (
E_{z}, H_{\phi}
) can propagate everywhere.