A Compact Dual-Band Dual-Polarized Antenna With Filtering Structures for Sub-6 GHz Base Station Applications

This letter presents a novel compact dual-band dual-polarized antenna with filtering structures for Sub-6 GHz base station applications. It is operating at the LTE (2500–2690 MHz) and Sub-6 GHz of 5G (3300–3600 MHz) bands, where the center frequency of upper-band (UB) is 1.32 times of lower-band (LB). Mutual coupling between LB and UB is suppressed by the introduction of the filtering stubs near the feeding lines. A sufficiently high isolation between LB and UB (>25 dB) is also obtained. The size of the proposed antenna is only 0.43 ${{\rm{\lambda }}_1} \times \text{0.43}$ ${{\rm{\lambda }}_1} \times \text{0.26}$ ${{\rm{\lambda }}_{1}}$ ( ${{\rm{\lambda }}_1}$ is the free-wavelength at 2.6 GHz). The half power beam widths are 65° ± 5° over both bands at horizontal planes. A four-element array, which consists of four hybrid antennas (the UB element is nested in the LB element) with a small array width (only 105 mm) is also studied. The proposed antenna and its array are suitable for wireless communication applications.