High-Order Characteristic Modes Suppression for Cross-Band Decoupling in Shared-Aperture Antenna Array

In dual-band shared-aperture base station antennas, the secondary radiation (SR) field caused by cross-band couplings always leads to radiation pattern distortion. In this work, the SR field caused by the coupling is attributed to the excitation of the target high-order modes from the perspective of the characteristic mode. To effectively suppress the target modes, L-shaped slots are proposed to load the arms of the radiator and altering the current paths. As compared with conventional dipoles without L-shaped slots, the proposed antenna generates less SR field. Therefore, the radiation pattern of the high-band antennas keeps stable in a dual-band shared-aperture antenna array environment. Prototype of a dual-band antenna array consisting of the proposed low-band (LB) antenna and a 4 × 4 high-band (HB) antenna array is fabricated. Simulated and measured results show that the designed dual-band array operates at both 0.74–0.82 GHz and 3.30–3.80 GHz. The experimental results verify that the cross-band decoupling has been achieved with the high-order mode suppression.