Radiation Characteristics of a Spheroidal Slot Antenna Coated with Isorefractive Materials

Abstract

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