Cross-Band Mutual Coupling Reduction in Dual-Band Base-Station Antennas With a Novel Grid Frequency Selective Surface

In this communication, a grid frequency selective surface (GFSS) is developed for cross-band near-field mutual coupling suppression. The unit cell of the GFSS consists of a break metal strip and a parallel LC resonator. The GFSS realizes low-stop property at 1.7-2.4 GHz (B1 band) and high-pass property at 3.3-3.8 GHz (B2 band). The novel GFSS is applied in a 5G dual-band antenna array with one B1 band antenna and four B2 band antennas. The cross-band mutual coupling coefficients are reduced from -14 dB to lower than -35 dB at the B1 band. Meanwhile, the radiation patterns of the B2 band antenna element are not affected due to the nonscattering feature of the GFSS. The dual-band base-station antenna array prototype is fabricated and measured to demonstrate the effectiveness of the proposed design in cross-band mutual coupling reduction.