Numerical analysis of stacked dielectric resonator antennas excited by a coaxial probe for wideband applications

The objective of the present study is to improve the bandwidth of the dielectric resonator antenna (DRA) excited by a coaxial probe by using a stacked DRA configuration above an infinite ground plane. The DRA is axisymmetric and a coaxial probe is placed off the antenna axis to excite the HEM_11δ mode in the DRA, resulting in a broadside radiation pattern. A surface integral equation formulation and the method of moments are used for the numerical analysis. The input impedance and the far field radiation patterns have been computed and the effects of different parameters on the antenna performance have been investigated. With the proper excitation and selection of the resonator parameters, a bandwidth of 35% has been achieved for the stacked DRA configuration based on a -10 dB reflection coefficient on a 50 Ω-transmission line. An equivalent circuit model is postulated to describe the dual-resonance behavior of the stacked antenna system.