Compact Single-/Dual-Polarized Filtering Dielectric Resonator Antennas

A compact single-polarized filtering dielectric resonator (DR) antenna (DRA) with high selectivity is investigated. The DRA is fed by hybrid microstrip line/conformal strip, excited in its fundamental TE y 1δ1 mode. Owing to the different loading effects of the microstrip stub and conformal strip, the resonance frequency of TE y 1δ1 mode excited by the two feed-lines is slightly different from each other. Such stepping resonances yield a wide bandwidth of 21.9% and a very flat gain of 5.1 dBi. The hybrid feeding scheme also establishes a cross-coupled structure in the DRA, which introduces two radiation nulls right near the band-edges. A compact wideband filtering DRA (FDRA) with quasi-elliptic bandpass response is therefore obtained without requiring any specific filtering circuit. This single-polarized design is also modified to realize a dual-polarized FDRA by adding another orthogonal port with same feeding scheme. To reduce mutual coupling between the two ports, the microstrip stubs are folded to L shape and four additional metal posts are inserted into the DR. As a result, the isolation is improved by 14 dB, from 7.2 dB to 21.2 dB.