Dual-Band Dual-Polarized Duplex Antenna Based on Stacked Filtering Element

In this letter, a dual-band dual-polarized antenna with duplex function is proposed. This antenna consists of the bottom lower-band (LB) element (1.805-1.88 GHz) and the higher-band (HB) element (2.11-2.17 GHz) in a suspend cavity, which covers the downlinks (DL) of 5G N3 and N1 bands with a narrow guardband of 11%. Both elements are designed with integrated filtering function, exhibiting radiation nulls at their respective higher and lower ends. The metal cavity is analyzed and optimized to minimize its blockage effect to the bottom LB element. By stacking the two elements coaxially, a dual-band duplex antenna with compact aperture size of 0.2 λ₀ is designed. As the LB element and the HB element are completely independent, the antenna features full band independence. By utilizing the high out-of-band suppression of the filtering element, without additional decoupling mechanisms, high cross-band isolation over 23 dB is achieved within a guardband of 11%. The simulated and measured results proved the proposed duplex antenna has features of dual-band operation, high cross-band isolation and compact aperture. These features make it suitable for duplex base-station antenna applications.