Radiation from an Axisymmetric Slot on a Spheroid Coated with an Isorefractive Material and Excited by a Delta Gap Source

This paper presents an analytic solution to the problem of radiation from an axisymmetric slot on a spheroid confocally coated with an isorefractive material, when the slot is excited by a delta gap source. The formulation is realized by expanding the electromagnetic field in each region in terms of spheroidal vector wave functions and a set of unknown expansion coefficients, and imposing boundary conditions at the interface between the surface of the spheroid and the isorefractive coating, as well as that between the coating and the medium exterior to the coating. This generates a set of simultaneous equations, the solution of which yields the unknown expansion coefficients. Results are presented as normalized power patterns and radiation patterns for both conventional isorefractive materials as well as for isorefractive metamaterials, to show the effects of the coating on the radiation from the antenna.