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.

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The dielectric overlay effects on the impedance properties of a radiating slot in the ground plane of a microstrip line are studied by using the reciprocity theorem and a moment‐method calculation. The Green's functions for the dielectric‐covered microstrip line‐fed radiating slot are given, and the expression for the slot impedance is shown. Numerical convergence of the moment‐method calculation using, respectively, piece‐wise sinusoidal basis functions and rooftop basis functions is discussed. Numerical results for the slot impedance as a function of overlay thickness and permittivity are presented and discussed. © 1994 John Wiley & Sons, Inc.

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