Rigorous computer-aided design of coaxial/circular antennas with semi-spherical dielectric layers

We present a new rigorous formulation for studying antennas made by a central circular waveguide, and a coaxial line; the circular waveguide being the inner part of the coaxial line. The antenna may be covered with spherically stratified dielectric layers for improving radiative properties. The use of spherical transmission lines provides the rigorous network representation of the antenna. It is shown that, by expressing the radiated field in terms of spherical modes, is advantageous for numerical computations and yields rigorous network representations. The proposed formulation moreover follows the same procedure used for discontinuities in closed waveguides, thus unifying the treatment of electromagnetic field propagation for guided and radiated wave problems.