A New Buffering Scheme for Shared-Aperture Dual-Band Base Station Antenna Array Utilizing Tight-Coupling Concept

A novel shared-aperture dual-band array based on a new buffering scheme is presented, with superior characteristics of an exceptionally low profile, stable dual-band radiation performance, and naturally suppressed cross-band interferences in 0.69–0.96 GHz (32.7%) and 1.47–2.7 GHz (59.0%). Unlike the previous shared-aperture array schemes that focus on reducing coupling between low-band (LB) and high-band (HB) antennas to address unwanted cross-band interferences, this array introduces a special tightly coupled buffering layer (TCBL) that is tightly coupled with both LB and HB radiators. The TCBL serves as a buffer, facilitating the radiation of both LB and HB antennas while mitigating cross-band interferences without requiring extra filtering/frequency-selective measures. It plays two crucial roles. In the LB, the TCBL functions as a reactance-compensation loading that enables a significantly low profile of the LB antenna. This leads to a reduced LB scattering influence on the HB antenna, realizing restored HB radiation performance. In the HB, the TCBL enables a new resonant mode that further expands the HB bandwidth from 45.5% to 59.0%. Meanwhile, the array effectuates effective cross-band isolation, as the TCBL prevents the electromagnetic energy from transferring to the cross-band ports. An array prototype was fabricated and tested, with measured results confirming the simulated ones.