Investigation on Rotated Rectangular Slots to Improve the Circular Polarization in Cylindrical Dielectric Resonator Antenna

To achieve wideband circular polarization (CP) characteristics, a new structure with a single feeding technique has been proposed. In the proposed CP structure, to excite the cylindrical dielectric resonator (CDR) four asymmetrical rectangular slots are etched on the ground plane, each rectangular slot is rotated by an angle of ( $\theta = 30^{\circ }$ ) with respect to its adjacent slots. The electric fields at each slot are separated by 30° in space with respect to its adjacent slot to create 90° angular separations between the E-field components. Two orthogonal broadside modes ( ${HE}_{11\delta }$ ) are excited inside the cylindrical dielectric resonator antenna (CDRA) independently to obtained CP characteristics. To compare the simulated outcomes with the experimental results, fabrication of the proposed antenna prototype has been done. The measured percentage of bandwidth achieved by the proposed radiator for $\vert \text{S}_{11}\vert $ and CP is 26.73% and 23.59%, respectively, and the whole usable axial ratio (AR) frequency bands overlap the impedance passband of the presented CP structure. The proposed radiator has achieved the maximum gain and radiation efficiency of 3.4 dB and 95% over the operating frequency range of the designed antenna, respectively. The proposed CP DRA has been configured for the WLAN band application