An Approach to Achieving Multiple Mutual Coupling Nulls in MIMO Stacked Patch Antenna for Decoupling Bandwidth Enhancement

To suppress mutual coupling among multiple-input multiple-output (MIMO) stacked patch antennas, a decoupling method achieving three mutual coupling nulls is proposed by utilizing one pair of symmetrical half-wavelength strips and a dual-hole single-pad structure. The first two mutual coupling nulls are caused by path cancellation after utilizing the two half-wavelength strips. The third one is triggered by phase cancellation of the driven and parasitic patches, and can be controlled by the dual-hole single-pad structure. Compared with the reported decoupling designs on stacked patch antennas, the proposed one can achieve wider decoupling bandwidth, higher isolation improvement, and no profile enhancement. The mutual coupling level of the two-element stacked patch antenna integrated with the proposed decoupling method can be decreased from −21.5 dB to −36.5 dB over the effective frequency range from 3.28 GHz to 3.6 GHz or 9.3%. Afterward, the proposed method is also proved to be effective in four-element stacked patch antenna.