Quad-Polarized Diversity Hollow Cylindrical Dielectric Resonator Antenna

This communication investigates a new quad-polarized diversity dielectric resonator antenna (DRA). The HEM
$_{31\delta }^{\mathrm {x}}$
, HEM
$_{31\delta }^{\mathrm {y}}$
, TE
$_{02\delta + 1}$
, and TM
$_{02\delta }$
modes of the cylindrical DRA are utilized. For a solid cylindrical DRA, the TM
$_{02\delta }$
-mode frequency is lower than those of the HEM
$_{31\delta }^{\mathrm {x,y}}$
and TE
$_{02\delta + 1}$
modes, which is an obstacle to the diversity design. In the central DR region, the E-field of the TM
$_{02\delta }$
mode is strong, but those of the HEM
$_{31\delta }^{\mathrm {x,y}}$
and TE
$_{02\delta + 1}$
modes are relatively weak. Therefore, decreasing the relative permittivity of that region by introducing a hollow can increase the TM
$_{02\delta }$
-mode frequency, with much smaller effects on the HEM
$_{31\delta }^{x,y}$
and TE
$_{02\delta + 1}$
modes. In this way, the frequencies of the DRA modes can be made closer to one another. A hollow cylindrical glass DRA is employed to demonstrate this idea. The broadside
${y}$
-polarized HEM
$_{31\delta }^{\mathrm {x}}$
and
${x}$
-polarized HEM
$_{31\delta }^{\mathrm {y}}$
modes are excited through two groups of notched aperture pairs. These four apertures are equally fed to excite the horizontally polarized omnidirectional TE
$_{02\delta +1}$
mode. Finally, a probe is used to excite the vertically polarized omnidirectional TM
$_{02\delta }$
mode. The proposed quad-polarized DRA has a minimum isolation of 21.4 dB and a peak gain of 3.57 dBi across the operation band. Additionally, its radiation patterns exhibit symmetry.