Wide-/Dual-Band Omnidirectional Filtering Dielectric Resonator Antennas

A wideband omnidirectional dielectric resonator antenna (DRA) with filtering response is investigated. The DRA is placed on a circular patch and excited by a hybrid feed that consists of a probe and a metallic disk. Two omnidirectional DR modes (TM_01δ and TM₀₁₃ modes) along with a patch mode and a probe mode are simultaneously excited by the hybrid feed, providing a broad bandwidth of 52.8%. The feeding scheme also establishes a cross-coupled structure in the DRA, which introduces a radiation null at the upper edge of the passband. A ring slot and four shorting pins are loaded on the patch to provide another radiation null at the lower edge of the passband. Consequently, a compact wideband filtering DRA (FDRA) with quasi-elliptic bandpass response is obtained without requiring specific filtering circuits. This wideband design is also modified to realize a dual-band FDRA. The metallic disk of the hybrid feed is moved to touch the upper DR face of the cylindrical hole. It divides the wide passband into two separate bands, giving a flat stopband between them. Four additional rectangular ring slots and shorting pins are fabricated on the ground plane to further widen the bandwidth and improve the filtering performance of the second band. As a result, a dual-band FDRA with the bandwidths of 10.1% and 3.73% is achieved. In each design, both the measured and simulated out-of-band suppression levels are about 15 dB.