Suppression of Cross-Band Resonance Coupling in Dual-Band Shared-Aperture Antenna Array

In dual-band antenna arrays, radiation patterns of low band (LB) antenna working in wide band might occur severe distortions and gain reduction with presence of adjacent high band (HB) antennas. Differing from the scattering from the LB antenna causing distortions in HB patterns and the coupling resulting in cross-band isolation degradation, this interference attributes to resonance coupling. To move resonance frequency point out of the target LB 0.69-1.00 GHz (36.7%), parallel resonance shifters are added between HB baluns and ground. Radiation patterns and realized gain within the LB are restored when the shifter-loaded HB antennas are present. In addition, this parallel structure has no adverse effect on the radiation and wideband matching of the HB antennas over 1.63-2.83 GHz (53.8%). A prototype of dual-band antenna array is fabricated, and measured results show good consistency with the simulated ones.