Self-Decoupled MIMO Antenna Pair With Shared Radiator for 5G Smartphones

In this article, a novel self-decoupled multiple-input multiple-output (MIMO) antenna pair with a shared radiator is proposed for fifth-generation (5G) smartphones. In our approach, a radiator is directly excited by two feeding ports, and interestingly, the two ports are naturally isolated across a wide bandwidth without using any extra decoupling structures. To offer a deep physical insight of the self-decoupling mechanism, a mode-cancellation method based on the synthesis of common and differential modes is developed for the first time. The proposed self-decoupled antenna pair shows a good isolation of better than 11.5 dB across the 5G N77 band (3.3-4.2 GHz) with a radiation pattern diversity property. Based on the self-decoupled antenna pair, an 8 x 8 MIMO antenna system, constituted by four sets of antenna pairs, is simulated, fabricated, and measured to validate the concept. The experimental results demonstrate that the proposed 8 x 8 MIMO system can offer an isolation of better than 10.5 dB between all ports and a high total efficiency of 63.1%-85.1% across 3.3-4.2 GHz. With the advantages of self-decoupling, shared radiator, simple structure, wide bandwidth, and high efficiency, the proposed design scheme exhibits promising potential for the future highly integrated MIMO antennas for 5G smartphones.