Numerical analysis of a biconical dielectric resonator antennas for wideband applications

Dielectric resonators are made of high dielectric constant materials and have been used efficiently as microwave components in filter design because of their high quality factor. Therefore, many engineers have doubted their usefulness as radiators, thinking that they would not be efficient radiators and that they would have very small radiation bandwidth. It has been shown, however that some modes have a small radiation Q-factor [1]. The radiation efficiency has also been predicted experimentally for the HEM11δ mode of a cylindrical dielectric resonator with ∈r=38. The radiation efficiency was found to be better than 98% [2]. Several research groups have studied the dielectric resonator antennas for different geometries using different numerical methods. In [3] an approximate magnetic cavity model is used to predict the resonant frequency and radiation patterns of cylindrical dielectric resonator antennas. In [4] the method of moments for bodies of revolution is used to accurately predict the radiation patterns. Also, the Green's function method is used to predict the input impedance and the radiation patterns for hemispherical dielectric resonator antennas excited by a coaxial probe or a narrow slot [5]–[6]. These studies helped us to understand the characteristics of this radiator better and showed the need for more accurate analysis methods. Therefore, the method of moments is used here to predict the input impedances of this antenna as in [7]–[8]. When the Finite-difference Time-domain method (FDTD) became mature, many references became available in the literature for such analysis [9], many of which cannot be listed here for brevity. The FDTD method can show us many of the characteristics of the antenna directly without the need for more processing of the data, such as resonant frequencies, field distributions, input impedance, and radiation patterns.