On the resonance and radiation characteristics of multi-layered spherical microstrip antennas

The resonance and radiation characteristics of a spherical microstrip with its circular metallic patch located inside a coating, possessing an arbitrary number of layers, are investigated. The developed methodology combines the Legendre transform with a T-matrix method The appropriate basis functions for the surface current on the patch are chosen according to the cavity model. The complex resonant frequencies are the singular points of a homogeneous linear system, resulting by following a Galerkin's technique. The numerical results of this article propose novel multi-layered spherical microstrip configurations. More precisely, a new type of excitation that concerns an amplifying layer located between core and patch is proposed The control mechanism of the amplifying capability via the layer's thickness and dielectric constant is reported Moreover the behavior of a microstrip with two airgaps that are surrounded by a zero-index material is analyzed Finally, a coating's continuous distribution, following a shifted Luneburg law, is treated by a step approximation of the radial function of its dielectric constant, and the achieved high quality factor of such a microstrip is discussed.