Analysis of a broadband slot-coupled dielectric-coated hemispherical dielectric resonator antenna

Dielectric-coated hemispherical dielectric resonator (DR) antennas fed by a microstrip line through a coupling slot are analyzed. The broadside TE₁₁₁ mode is studied, and the reciprocity theorem is applied in this analysis. In this case the dielectric-coated DR antenna can be viewed as a series load at the slot position as seen by the microstrip line. The impedance of this series load is calculated by using a Green's-function formulation, and the input impedance of the slot-coupled DR antenna can then be obtained using transmission-line theory. Numerical results for the input impedance are calculated and presented, and the antenna bandwidth is discussed. It is observed that the antenna bandwidth of a dielectric-coated DR antenna can be as high as two times that of a DR antenna without a coating.