In-Band Mutual Coupling Suppression in Dual-Band Shared-Aperture Base Station Arrays Using Dielectric Block Loading

Dual-band base station antenna (BSA) arrays with shared aperture have attracted considerable attention for the fifth-generation (5G) communication. The focus is mainly on decoupling between lower band (LB) and higher band (HB) antennas (i.e., cross-band decoupling). The in-band BSA decoupling techniques are usually not applicable to broadband dual-band shared-aperture BSA arrays. HB BSAs' elements usually are separated by more than half-wavelength to reduce the in-band mutual coupling, which increases the array aperture and causes grating lobes for beam steering. Here, a novel decoupling technique of dielectric blocks is proposed to suppress the in-band couplings in dual-band shared-aperture BSA arrays. The dielectric blocks are placed above the HB elements to neutralize the original coupling by creating partially reflected waves (an addition wave path). A compact interleaved dual-band BSA array with dielectric blocks is designed and manufactured. The LB operates between 1.9 and 2.5 GHz, and the HB covers the 5G band from 3.3 to 3.9 GHz. The HB coupling is effectively reduced below-25 dB, while the impedance matching and radiation performance of the HB and LB elements are maintained. Moreover, the dielectric blocks are implemented for stacked and interleaved dual-band BSA arrays with suppressed cross-band interference. The proposed decoupling method has simple structures, easy to design and fabricate, and is compatible with the existing cross-band decoupling techniques for different dual-band BSA array configurations.