Tri-band Dual-Polarized Shared-Aperture Antenna for 2G/3G/4G/5G Base Station Applications

This paper presents a novel tri-band, dual-polarized and shared-aperture antenna with frequency selective function for Sub-6 GHz base station applications. The proposed antenna is composed of a dual-polarized square loop antenna with two parasitic loops for 2G/3G/4G (1710-2690 MHz) and a differentially fed dual-polarized planar antenna for 5G (3300-3600 MHz and 4800-5000 MHz) base station applications. These two antennas are placed coaxially but different altitude for saving the installation space. In order to achieve good individual performance for these two antennas in the same aperture without interference or blocking, the lower-band (LB) antenna is designed as a frequency selective surface (FSS) for the nether mid/upper-bands (M/UBs) antenna. Measured results show that the proposed antenna achieves a high port isolation (> 20 dB) between LB and M/UBS and a -10-dB impedance bandwidth of 50.4% (1.60-2.70 GHz), 14.9% (3.28-3.80 GHz) and 8.6% (4.75-5.18 GHz), respectively. To further validate the design concept, an antenna array composed of 4 LB elements and 8 M/UBs elements with correspond spacing is fabricated and measured, which demonstrates the application of the tri-band shared-aperture antenna in array form.