The admittance of a monopole antenna fed through a ground plane by a coaxial line

A solid circular cylindrical monopole fed through a perfectly conducting ground plane by a coaxial line is rigorously analyzed by applying full wave field theory using the conservation of complex power technique. The model of this analysis is the structure of a coaxial line feeding a larger coaxial waveguide terminated in a ground plane. As the outer radius of the coaxial waveguide is increased, the transverse electromagnetic (TEM) mode admittance of a cylindrical monopole radiating over a ground plane is estimated using a variable bound approach. Numerical results for a thin monopole are established and compared with R.W.P. King´s (1971) results for the tubular one. Results for a thick monopole fed by its coaxial line having the dielectric constant ε_r are also given