Compact Cylindrical Pattern-Diversity Dielectric Resonator Antenna

A compact cylindrical pattern-diversity dielectric resonator antenna (DRA) is designed using the HEM_11δ and TM_01δ modes, which are the fundamental modes of the hybrid electromagnetic (HEM) and TM modes, respectively. To make the two resonance frequencies equal for the diversity operation, a meander-line-loaded annular slot is used to excite the TM_01δ mode and to lower its resonance frequency. The annular slot, however, does not significantly affect the HEM_11δ mode, which is excited by a pair of differential strips. It is found that impedance match of each port can be tuned independently. To verify the idea, a 2.4 GHz prototype was designed, fabricated, and measured for WLAN applications. Good agreement between the measured and simulated results is observed. The impedance passbands of the two modes have an overlapping bandwidth of 5.7%, with the port isolation higher than 30 dB. The envelope correlation coefficient obtained from the measured field patterns is desirably very low, being less than 0.001. Our design is electrically smallest in volume and lowest in profile among the reported pattern-diversity DRAs.