FDTD analysis of modal characteristics of dielectric resonator antennas

Dielectric resonator (DR) antennas have many desirable features, such as low cost, low profile, high radiation efficiency, large operating bandwidth and low losses, which make them prospective devices for millimeter wave applications. One of the most useful features of the DR antennas is their ability to produce multiple radiation patterns via the excitation of different resonant modes. While these modes in spherical and cylindrical DRs have been well studied, there is little information available in the literature about the modes in the rectangular DRs. We apply the FDTD method to study the resonant modes in rectangular DR antennas. Standing wave patterns of electric and magnetic field components have been simulated and the mode charts for different mode types constructed. The resonant fields in DR antennas are equivalent to those created by combinations of magnetic or electric dipoles located in the DRs. The possibility to excite TM modes in rectangular DR antennas is demonstrated and it is shown that higher order TM modes can function as arrays of vertical electric dipoles that can be used to design DR antennas with radiation along the azimuth plane.