Aperture Reduction Using Downward and Upward Bending Arms for Dual-Polarized Quadruple-Folded-Dipole Antennas

A method to miniaturize the aperture of a dual-polarized quadruple-folded-dipole (QFD) antenna by bending its arms downward or upward is proposed in this letter. Two practical prototypes called downward-bending-arm (DBA) antenna and upward-bending-arm (UBA) antenna are presented and elaborated. Both the DBA and UBA antennas have four pairs of arms bent downward or upward along the four edges of the planar QFDs, respectively, which enable the aperture of the DBA and UBA antennas to shrink to around $0.24{\lambda }_0 \times 0.24{\lambda }_0$ ( ${{\rm{\lambda }}}_{0}$ is the free-space wavelength at 2 GHz). Both antennas can achieve relatively small apertures while ensuring good matching, isolation, and radiation performances within the band of interest. Especially, the DBA antenna has a lower profile than the UBA antenna while the UBA antenna outperforms the DBA antenna in realized gain by approximately 1 dB. Meanwhile, the UBA antenna has narrower half-power beam width, which will be beneficial in compact massive multiple-input–multiple-output antenna arrays for improved radiation patterns.