Study of the shaped probe on the cup dielectric resonator antenna for bandwidth enhancement

Dielectric resonator antennas (DRA) are attractive at high frequencies. They can be designed with different shapes, but have the drawback of narrow bandwidths, typically around 10%. A wide range of materials is available to control the size and the bandwidth. One method of excitation is the coaxial probe, which is usually placed inside the DRA. It can be difficult to drill a small hole for the probe in ceramic materials, especially if the hole is close to the wall. Deformation of the DRA geometry from regular shapes can be used to enhance the bandwidth. Instead of drilling a small hole in the DRA, we modify the shape of the DRA to contain an easily machined groove which is large enough to house the shaped probe. Several probe shapes are investigated. It is found that L-, J- or hook-shaped probes can enhance the bandwidth of the DRA and excite a broadside-radiating mode. A single probe achieves a bandwidth around 30%. Using two orthogonal probes excites two orthogonal modes for dual polarization and further enhances the bandwidth. A wideband dually polarized DRA was studied and a bandwidth of 30-50% was achieved.