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Stacked Conical Ring Dielectric Resonator Antenna Excited by a Monopole for Improved Ultrawide Bandwidth

Stacked conical ring dielectric resonator antennas (DRA) excited by an axi-symmetric coaxial monopole are investigated numerically and experimentally for improved bandwidth. The bandwidth improvement is due to an extra resonance which occurs near the frequency where the monopole height is about a full wavelength. We consider two cases of the hybrid antenna: one case in which the tips of both cones face up and a second case in which the top cone is inverted to form a “sand-glass” shaped DRA. Measured data were obtained to validate the results of simulations. The proposed hybrid antennas can easily offer a fractional impedance bandwidth up to 138% along with monopole type radiation pattern. The antennas have a relatively low peak gain around the extra resonance.