Differential-Fed Dual-Polarized Filtering Fabry-Perot Antenna With High Isolation

In this paper, a dual-polarized filtering Fabry-Perot antenna (FPA) with high-isolation is proposed. It consists of a feed element of differential-fed dual-polarized square patch and a partially reflecting surface (PRS). The patch is capacitively coupled with T-shaped resonators and shorting-vias to obtain broadband characteristic and radiation nulls. The PRS structure is composed of two complementary metasurface layers, which are selected for achieving a positive reflection phase gradient within the broad frequency range. More interestingly, thanks to the frequency selectivity feature, the PRS significantly enhances the filtering characteristic of the FPA. For verification, a prototype of the proposed antenna operating at the 5.5-GHz center frequency has been fabricated and measured. The prototype with an overall size of <inline-formula> <tex-math notation="LaTeX">$\sim 2.0\lambda _{\text {min}} \times 2.0\lambda _{\text {min}} \times 0.49\lambda _{\text {min}}$ </tex-math></inline-formula> (<inline-formula> <tex-math notation="LaTeX">$\lambda _{\text {min}}$ </tex-math></inline-formula> is the free-space wavelength referring to the lowest operational frequency) result in an impedance bandwidth of 17.1% (<inline-formula> <tex-math notation="LaTeX">$5.02-5.96$ </tex-math></inline-formula> GHz) for 10-dB return loss and a high isolation of <inline-formula> <tex-math notation="LaTeX">$\ge45$ </tex-math></inline-formula> dB. Moreover, the far-field measurements result in a good dual-polarized radiation with the peak gain of 13.0 dBi, cross-polarization level of <inline-formula> <tex-math notation="LaTeX">$\le $ </tex-math></inline-formula>–25 dB within the passband, and out-of-band suppression level of <inline-formula> <tex-math notation="LaTeX">$\ge20$ </tex-math></inline-formula> dB.