This letter presents a dual-polarized, band-pass filtering antenna, or “filtenna” with a steep roll-off rate and a compact size. To simultaneously support multiple communication standards in a shared aperture, base station antenna arrays need to operate in multiple closely-spaced frequency bands. However, each filtenna has a limited space in the aperture-shared array; therefore, it is challenging to achieve a high roll-off rate. To resolve this problem, we proposed a filtenna that consists of four stacked X-shaped patches, of which the second from the bottom is the driven patch and the rest are parasitic ones. These closely coupled parasitic patches switch rapidly from resonance to antiresonance; however, their radiations change because they together cancel one another and create a very steep roll-off rate. The aperture dimension of the proposed antenna is $0.2 \, \lambda _{0} \times 0.2 \, \lambda _{0} \times 0.14 \, \lambda _{0}$, where $\lambda _{0}$ is the wavelength in free space at the center frequency. The measurement results demonstrate a very steep roll-off rate up to 1795 dBi/GHz at the lower cutoff frequency of 1.8 GHz. The measured average gain was 8 dBi over the operating frequency band of 1.805–1.88 GHz, which makes the proposed filtenna a good candidate for multiband and multistandard base stations.

中文翻译：

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用于基站的具有陡峭滚降率的紧凑型双极化滤波器

这封信介绍了一种双极化带通滤波天线，或“filtenna”，具有陡峭的滚降率和紧凑的尺寸。为了在共享孔径中同时支持多种通信标准，基站天线阵列需要在多个紧密间隔的频带中运行。然而，每个filtenna在共享孔径阵列中的空间有限；因此，实现高滚降率具有挑战性。为了解决这个问题，我们提出了一种由四个堆叠的 X 形贴片组成的 filtenna，其中倒数第二个是驱动贴片，其余的是寄生贴片。这些紧密耦合的寄生贴片迅速从共振切换到反共振；然而，它们的辐射会发生变化，因为它们一起相互抵消并产生非常陡峭的滚降率。$0.2 \, \lambda_{0} \times 0.2 \, \lambda_{0} \times 0.14 \, \lambda_{0}$， 在哪里$\lambda_{0}$是中心频率处自由空间中的波长。测量结果表明，在 1.8 GHz 的较低截止频率下，滚降率高达 1795 dBi/GHz。在 1.805-1.88 GHz 的工作频带上测得的平均增益为 8 dBi，这使得所提出的 filtenna 成为多频带和多标准基站的良好候选者。