Decoupling and Low-Profile Design of Dual-Band Dual-Polarized Base Station Antennas Using Frequency-Selective Surface

A dual-band dual-polarized base station antenna array is developed for fifth generation (5G) applications. Low-profile characteristic, high isolations, and shared-aperture are realized by introducing a frequency-selective surface (FSS) between radiators operating in the 0.69-0.96 GHz (B1) and 3.5-4.9 GHz (B2) bands. The dual-polarized B1-band antenna has a low-profile height of 0.12 lambda(L) (lambda(L) is the wavelength at the center frequency of B1). As for the B2 band, a 2x2 dual-polarized array sharing the same aperture with the B1-band antenna is developed for the sub-6 GHz band. Severe mutual coupling between B1- and B2-band antennas is reduced by the FSS. High port isolation (>25 dB) between B1- and B2-band antennas is achieved. A prototype consisting of one B1-band antenna and a 2x2 B2-band antenna array is fabricated. Measured results show that the proposed dual-band dual-polarized array achieves 32.7% and 33.3% bandwidth in the B1 and B2 bands, respectively. Measured results also demonstrate that the proposed array offers stable radiation patterns, high gains, and high cross-polarization discriminations (XPD > 20 dB) across the two frequency bands. These attractive features make this array an ideal candidate for future 5G massive MIMO base station antenna developments.