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.

A probe‐fed hemispherical dielectric resonator antenna with a dielectric coating is investigated rigorously by using a Green's function formulation. Numerical results for the input impedance at TE111 mode are calculated. It is found that, by coating the dielectric resonator antenna with a dielectric material having a relative permittivity about half that of the dielectric resonator antenna, the impedance bandwidth of the antenna can be significantly improved. This dielectric coating here serves as a transition region between the wave inside the dielectric resonator antenna and the free‐space wave, and thus can increase the impedance bandwidth of the antenna. A broadband dielectric resonator antenna can thus be obtained. © 1994 John Wiley & Sons, Inc.

As an example, the dual-reflector antennas of spheroidal wave function distribution and uniform distribution have been used. For spheroidal wave function distribution, we have obtained transmission efficiency of nearly 95%, whereas for the uniform distribution, only 80% has been obtained. CONCLUSIONPrinciples of geometrical optics are used to design dualreflector antennas with nonuniform amplitude and phase distributions, which can achieve maximum power transfer. Such antenna systems have value in the field of materials metrology, especially for dielectric measurements, and where maximum power transfer is required. ABSTRACT The theoretical approach based on a combination of the reciprocity theorem and a moment-method calculation has been applied in the analysis of an inclined printed slot antenna and an inclined-slot-coupled dielectric resonator antenna. The input impedance of the antenna is formulated and calculated. The obtained theoretical results are found to be in good agreement with the experimental data. This theoretical method is good for solving the inclined printed slot and inclined-slot related problems. 0 1996 John W i l e y ABSTRACT The purpose of this communication is to discuss the effect of the mutual coupling between element arrays on the radiation pattern, and to compensate for this effect in introducing them into a power far-jield pattern synthesis array. The synthesized pattern is an optimum approximation to the prescribed power pattern in the minmax sense. A study is realized for shaped seciarian and cosecant beams. 0 1996 John Wiley & Sons, Inc.

Rigorous full-wave analysis of a slot-coupled hemispherical dielectric resonator antenna has been recently reported [ 11. This kind of slot-coupled DR antennas has the advantage of mechanical simplicity and avoids large probe self-reactances, as compared to a probe-fed DR antenna. In this paper, we extend the study of a hemispherical shape to a multilayered hemispherical configuration. The geometry of a two-layered hemispherical DR antenna with slot coupling is shown in Fig. 1, where the permittivity of the outer-layer dielectric is chosen to be about half that of the inner-layer dielectric [2]. In this case, the outer-layer dielectric can be served as a transition region between the air and the inner-layer dielectric, and thus can increase the bandwidth of the antenna. To accurately determine the antenna bandwidth, the input impedance of the slot-coupled DR antenna is derived using the reciprocity theorem [3] and a Green's-function fonnulation [ 1],[2]. Numerical results are then calculated using a moment-method calculation: TheoryBy applying the reciprocity analysis [3],[4], the unknown equivalent magnetic current in the slot is first expanded using piecewise-sinusoidal (PWS) functions, and the DR antenna can be treated as a series load at the slot position as seen by the microstrip feedline. The coupling slot of length L and width W (L >> W) is assumed to be centered below the DR antenna, which makes the broadside TE,,, mode radiation the strongest [l]. Then, to calculate the input impedance seen by the microstrip feedline, the total admittance at the slot discontinuity needs to be evaluated. This admittance (Y, = Yf + Yh is calculated from the microstrip feedline contribution (U,) and the multilayered DR antenna contribution (YJ To determine Yf and Yo both the Green's functions for the $-directed magnetic field at the slot position (x, y, 0) on the feedline side and on the antenna side are derived.