Comparison of the Performance of Double-Step Rectangular Dielectric Resonator Antennas

In this paper, numerical and experimental investigations on various wideband Dielectric Resonator Antennas (DRAs) are reported. The coaxial-fed two-step rectangular DRA has been proposed as a wideband antenna, characterized by easy fabrication, wide impedance bandwidth and stable radiation characteristics. Its operation relies on the excitation of multiple modes at nearby frequencies in order to obtain a wide impedance bandwidth through the overlap of their resonances. Here, this operational concept is further enhanced. It is shown that the impedance bandwidth of "flipped" double-step DRAs is significantly improved, due to the decrease of the radiation Q-factor of the excited modes. Therefore, similar DRAs may present a very different performance for the same feeding scheme and excited modes, depending on the DRAs\´ orientation with respect to the ground plane.