Novel Frequency-Reconfigurable and Self-Decoupling Technique for MIMO Antenna Systems Leveraging Flexible Air Cavities

A novel and effective method for frequency reconfiguration and self-decoupling is proposed for multiple-input–multiple-output (MIMO) antenna systems in this letter. As a demonstration, a two-patch antenna system is designed and achieves six reconfigurable states by adjusting the heights of the flexible cavities, corresponding to different resonant frequencies and coupling efficiencies. The electromagnetic energy can be confined within each cavity by elevating the cavities, leading to superior port isolation. The design is validated through prototype fabrication and testing, with the measured results closely aligning with the simulations. The highest port isolation, exceeding 17.6 dB, is achieved when both dielectric patch antennas (DPAs) are in the up state. This corresponds to a maximum coupling reduction of 6.49 dB compared to the scenario where both DPAs are in the down state. The proposed approach achieves high port isolation without the need for additional decoupling structures and enables frequency reconfiguration, offering a simple and efficient solution for emerging MIMO systems.