Design of a novel compound decoupling structure for multiple-input multiple-output antenna array

A novel compound structure made up of Y-shaped microstrip interdigital lines, slots etched into the ground plane and metallized vias embedded in the substrate is designed to enhance the isolation between H-plane antenna array elements in this paper. Also, the operating mechanism of the decoupling structure is detailedly analyzed, as it can transform the coupling mode and suppress the transmission of surface current from one port to another. Then, after inserting the structure into the coupled antenna array, whose edge-to-edge distance between antenna elements is only 4 mm (0.07 lambda(0)), a 32.2 dB reduction of mutual coupling at the operating frequency 5.25 GHz is obtained. Moreover, the H-plane radiation pattern is modified, the radiation gain is increased, and the diversity performance is improved. Simulated results are in good accordance with measured results, verifying decoupling effectiveness of the proposed structure. The proposed structure has high feasibility in the utilization of MIMO or the wireless Rx/Tx system.