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In this article, a simple dual-polarized antenna with filtering responses and enhanced bandwidth is proposed for base station applications. The antenna concludes three parts: dipole elements, baluns, and a ground plane, which is the same as that of a widely used traditional base-station cross-dipole antenna. By employing only two parasitic elements without using very complicated circuits, the proposed dual-polarized antenna achieves not only filtering response but also widened bandwidth. Each parasitic element produces one transmission zero at higher frequency for the polarization it is associated with, while the other parasitic element produces another transmission zero at lower frequency band for the perpendicular polarization. The two introduced radiation nulls near the passband edge are also controllable. The working mechanism for achieving filtering responses is given. To demonstrate the idea, a simple dual-polarized filtering base-station antenna element is fabricated. The proposed antenna obtains 63% (1.68–3.23 GHz) impendence bandwidth with voltage standing wave ratio (VSWR) less than 1.5. The antenna also features good isolation of more than 32 dB and stable beamwidth variation of less than ±5°. The measured gain within working band is around 8.5 dBi, while the radiation suppression level in stopband is 13 dB. [ABSTRACT FROM AUTHOR]

This paper presents a broadband dual-polarized filtering dipole antenna for base-station application, which has a compact size of 50 $\text {mm} \times 50\,\,\text {mm} \times 31.8$ mm. The antenna consists of four parts: main radiator, feeding baluns, reflector, and two parasitic loops. Without using complex filtering circuits, the dual-polarized dipole antenna realizes satisfactory filtering performance and enhanced bandwidth by employing only two parasitic loops. Two specific radiation nulls are thus generated and individually controlled by the two parasitic loops. To further improve the upper stopband selectivity and bandwidth, a simple open-ended stub is added to the arms of the dipole. As a result, the bandwidth can be tuned from 7.4% to 47.6%, and the realized gain is decreased dramatically from 8.6 dBi at 2.7 GHz (in-band) to −10 dBi at 2.9 GHz (out-of-band). For demonstration, a broadband dual-polarized dipole antenna is implemented. Measured results show that the proposed antenna has more than 34 dB port isolation over 48.7% (1.66–2.73 GHz) impendence bandwidth (VSWR < 1.5). The measured in-band gain is about 8.15 dBi with stable 3 dB beamwidth 65.4°±2.4° in the horizontal plane, whereas the out-of-band radiation suppression is more than 17 dB. [ABSTRACT FROM AUTHOR]