Theory and experiments on horizontally inhomogeneous Rectangular Dielectric Resonator Antenna

A theoretical investigation on horizontally inhomogeneous Rectangular Dielectric Resonator Antenna (RDRA) is presented here using the mode matching technique. The inhomogeneous permittivity is introduced by placing two RDRA segments of different materials horizontally side by side. The fundamental TE111y mode is investigated here. Eigenfunction, eigenvalue, resonant frequency and far-field radiation patterns are presented. A closed form analytical expression is given here to predict the resonant frequency. Four antenna prototypes are fabricated and tested for experimental validation. It is found that our theoretical results are in good agreement with experimental data, published data as found in the open literature and data obtained using the 3D EM simulator. It is also found that Horizontally Inhomogeneous RDRA (HIRDRA) produces a peak in the broadside direction at fundamental TE111y mode. It is found that our theory gives results order faster (approx. 400-600 times) than commercially available 3D numerical EM simulator HFSS. The inhomogeneity introduces additional two degrees of freedom (width and permittivity of the additional dielectric segment) which give more flexibility to the antenna design, leading to wider tuning range over conventional RDRA. Advantages of this novel antenna structure are discussed in detail. This theory can easily be extended to investigate fractal shaped RDRAs, log-periodic antenna using RDRAs.