Recent Trends in the Design and Development of Dielectric Resonator Antennas

Dielectric resonators (DRs) had been popular while designing oscillators and filters where they act as energy-storing element in the shielded environment. DRs possess unique properties such as low losses, high permittivity, and thermal stability. Possible geometries can be rectangular, cylindrical, spherical, etc. Investigation of DRs as efficient radiators started in the year 1983 when cylindrical, rectangular, and hemispherical shapes were experimentally verified by Long et al. Excitation of resonant modes, radiation characteristics, and techniques of excitation were studied for the three aforementioned basic geometries. Interestingly, dielectric resonator antennas (DRAs), irrespective of their geometries operating at their fundamental modes, behave like a short horizontal magnetic dipole. The demand for wide bandwidth, compact design, high gain, and radiation efficiency for modern communication resulted in the development of wideband and multiband antennas. These antennas could meet the stringent requirements of the modern communication system. However, to overcome the problem of limited bandwidth and bulky size particularly at lower frequencies, various DRAs that are irregular in shape have been developed. These shapes are inspired from three basic geometries, viz., cylindrical, rectangular, and hemispherical.