Wideband Cup Dielectric Resonator Antenna With Stable Omnidirectional Patterns

A wideband omnidirectional cup dielectric resonator antenna (CDRA) is designed by utilizing three modes (DR TM01δ, coil, and monopole modes) for the first time. It deploys the modified coil feeding structure comprising four coil segments and two close-by probes. The four coil segments provide an equivalent magnetic-current loop and the two probes act as an electric monopole. Thus, the modified feeding structure can excite the DR TM01δ mode and two neighbor resonances extending the operating bandwidth. All of these modes have omnidirectional characteristics. To verify the idea, a CDRA is designed, fabricated, and measured. The CDRA is 0.61λ0×0.32λ0 (where λ0 is the free-space wavelength at the center frequency) with a bandwidth of 67.7% (3.28-6.64 GHz). The antenna has stable omnidirectional radiation patterns, high radiation efficiencies, and a low cross-polarized level within the operating bandwidth.