Compact self-Isolated MIMO antenna system with low mutual coupling for 5G mobile applications

In this paper, a compact self-isolated 4-antenna multiple-input-multiple-output (MIMO) is proposed for the fifth-generation (5G) mobile applications. The proposed design is composed of inverted U-shaped, feeding element T-shaped, two circular-ring radiators and two stubs aligned together in a specified location based on the distance of L2 and H2. The compact size reduction introduced in this design is due to the alignment of the circular-rings with the vertical stubs and the microstrip line feeding. The proposed compact size of the selfisolated 4-antenna MIMO system offers very good isolation without using any decoupling techniques, indicated by the transmission coefficients which reach above -30 dB for S12, S32, S34 and S23 for λ/4 and reaches above -20 dB for λ/14. Besides, the result values for reflection coefficients display significant performance reaches above -50 dB for λ/4 and -38 dB for λ/14 which indicates the good performance of the compact MIMO antennas, despite varying the distance and despite its arrangement on a high loss FR-4 dielectric substrate. The MIMO antenna offers significant features to be used in 5G mobile applications.