A New Self-Decoupling Structure on Coupling Compensating Technique for MIMO Patch Antennas

In this article, an effective self-decoupling solution for MIMO patch antennas is proposed based on the capacitive and inductive coupling compensating technique. Initially, the coupling principles for the original coupled antenna array are studied, and the decoupling condition for two closely spaced patch antennas in the H-plane is obtained. Subsequently, a concise decoupling element composed of six pairs of shorting pins is developed. Herein, four pairs of shorting pins deployed at the corners of the patches aim to introduce additional inductive coupling to effectively suppress mutual coupling between adjacent antennas, whereas the remaining two pairs of shorting pins, together with the etched slots, are designated to introduce additional capacitive coupling and reduce the cross polarization. To verify the feasibility of the proposed self-decoupling scheme, prototypes of two-element patch antennas are respectively constructed and tested before and after applying the self-decoupling design. Results reveal that, in comparison with the coupled array, the isolation between two self-decoupled elements is improved from 10.5 dB to 17.5 dB at the center frequency of 4.85 GHz with an extremely close edge-to-edge separation of 0.007 λ0. Furthermore, owing to the single-layer layout, the overall antenna profile is maintained at a relatively low height of 0.04 λ0. Ultimately, the proposed decoupling scheme is also theoretically validated in three-element and E-plane arrays, demonstrating effective isolation enhancement for large-scale compact patch configurations.