Self-isolated MIMO antenna using mixed coupling by close coupling technique

A self-isolated multiple-input-multiple-output (MIMO) antenna in a compact shared ground structure is proposed for 5G systems. The proposed MIMO antenna consists of customized M-pattern, closely coupled members. It benefits to attain good isolation of the targeted bandwidth transversely without additional de-coupling structures. It is discovered that the arm of M-pattern antenna members can cancel out the coupling on the system and achieve sound isolation among antenna members. A relevant matching circuit model is discussed to show how the suggested theory works in principle. The mixed couplings among antenna members neutralize by modifying the antenna shape with the help of electric and magnetic coupling and surface currents. The proposed self-isolated 2-member MIMO antenna demonstrates sound isolation superior to 15 dB transversely in the frequency bands dedicated to 5G NR: n48/n78 and long-term evolution (LTE) band 42/43/48/52 (3.2–3.98 GHz). Moreover, the proposed 2-member design structure has a scalability advantage. It is extended into an 8-members structure, where a pair of antennas located at each side of the frame offers orthogonality. The proposed 8-members M-pattern MIMO is validated using fabricated and simulated measurements. The investigational results show that the 8-members MIMO (M-shaped) system is effective in higher order MIMO antenna design and offers more than 20 dB isolation transversely in the frequency band 5G NR n48 and LTE band 42/43/52(3.29–3.66 GHz).