A Metasurface-Based Dual-Polarized Filtering Antenna With High Isolation and Wide Out-of-Band Suppression

This letter presents a novel compact dual-polarized filtering antenna (DPFA) based on a metasurface (MTS) structure. By integrating a 3×3 MTS array, a cross-shaped slot-etched ground plane, and orthogonally placed microstrip feedlines, the proposed antenna achieves filtering and polarization diversity performance, significantly enhancing out-of-band suppression level while maintaining a low-profile structure of just 0.045λ₀. The modified Π-shaped stubs on the microstrip feedlines generate the radiation null on the left side of the passband, while the MTS generates the radiation null on the right side of the passband. Thus, the proposed DPFA realizes an out-of-band suppression level of more than 23 dB and a wide out-of-band suppression up to 2.2f0. Without employing differential feeding, the proposed DPFA attains isolation levels greater than 32 dB and cross-polarization discrimination (XPD) above 25 dB, thereby ensuring robust polarization diversity performance. Furthermore, the antenna offers a wide impedance bandwidth (IBW) of 20.41% (3.30–4.05 GHz), covering n78 spectrum band. Due to its integrated filtering capability, high isolation, and compact size, the proposed DPFA meets the requirements for miniaturized and high-performance antennas in wireless communication infrastructure.