Source exciation effects on power radiation from material and metamaterial resonances

The radiated power from a slotted spherical dipole antenna coated with dual layers of materials and metamaterials is determined. The excitation is assumed to be due to a constant applied voltage at the slot. It is shown that the radiated power is dependent on the coating parameters and, in particular, it can increase dramaticallyi at the mode resonances. The problem is solved using a boundary value problem formulation, and determining the mode coefficients, using a matrix inversion. It is found that, at mode resonances the coefficients of the resonating mode becomes excessively large, and the radiation is due to the resonant mode alone. Using this finding, it is shown that the computed excessive radiated power is due to the assumed slot excitation, which can occur with any coating material when a particular mode becomes resonant.