An In-Band and Cross-Band Decoupling Patch Antenna Array With Improved Isolation and Reduced ECC

This paper proposes a method to simultaneously suppress in-band and cross-band mutual coupling in MIMO patch antenna arrays. The proposed approach uses a short-circuited stub loaded half-wavelength strip resonator to couple patch antenna, achieving mutual coupling and radiation nulls. When the short-circuit stub loaded half-wavelength resonator operates in odd mode, it couples with the metal patch to form the radiation band and generate an upper radiation null. When the resonator operates in even mode, it generates a lower radiation null, enabling filtering characteristics that reduce cross-band mutual coupling. The loading of short-circuit stubs also adjusts the antenna's initial phase, and combined with the path superposition effect, mutual coupling null is generated, reducing in-band mutual coupling. Compared to the existing designs, the proposed approach is more compact, offers better isolation, and achieves both cross-band and in-band decoupling on a 2-D array. Additionally, it provides the extra benefit of reducing the Envelope Correlation Coefficient (ECC). To verify the effectiveness of the proposed method, an antenna array was fabricated and measured. The 10-dB impedance bandwidths for the antenna elements operating at 3.5 GHz and 3.8 GHz are 2.84% and 3.42%, respectively. The in-band isolation exceeds 31.3 dB, the cross-band isolation exceeds 30.8 dB, and the ECC within the operating band is less than 0.0005.