Omnidirectional Dielectric Resonator Antenna with a Planar Feed for Circular Polarization Diversity Design

The cylindrical dielectric resonator (DR) antenna (DRA) is excited in its omnidirectional TM _011δ mode by a planar shorted microstrip cross. With this nonintrusive feed, the DRA can be fabricated without the need of drilling a hole in the DR as required in the probe feed method. This DRA is applied to the first omnidirectional circularly polarized (CP) diversity DRA. To generate omnidirectional CP fields, the TM _011δ and TE _011+δ modes are excited simultaneously. The TE_011+δ mode is excited by four microstrip arcs. They provide a pair of equivalent magnetic dipoles that generate fields that are orthogonal to those of the TM _011δ mode. Omnidirectional CP fields can be obtained when the (orthogonal) fields of the TM _011δ and TE_011+δ modes are equal in amplitude but in phase quadrature. In our two-port CP diversity design, phase differences of +90° and-90° are obtained in ports 1 and 2 to generate right- A nd left-hand CP fields, respectively. Prototypes at 2.4 GHz were designed, fabricated, and measured for WLAN applications. The S-parameters, radiation patterns, antenna gains, and efficiencies are studied. For the diversity design, the axial ratio, envelope correlation coefficient, and mean effective gain are also obtained. The measured and simulation results are in reasonable agreement.