Tightly Arranged Four-Element MIMO Antennas for 5G Mobile Terminals

In this paper, a compact multiple-input multiple-output (MIMO) antenna is presented for 5G mobile terminals. The antenna consists of four tightly arranged elements and three lumped components. The edge-to-edge distance between adjacent elements is only 1 mm. It is found that adding an inductor at the current minimum location or a capacitor at the current maximum location of two elements can significantly reduce the mutual coupling. Based on high-isolated dual-element structures, a four-element MIMO antenna is experimentally analyzed for 3400–3600 MHz band. The size of the antenna is only <inline-formula> <tex-math notation="LaTeX">$40.8 \times 3$ </tex-math></inline-formula> mm<sup>2</sup>. The measured −6 dB bandwidth of the antenna is 135 MHz, with port isolation higher than 11.6 dB. In addition, a vertically placed four-element MIMO antenna is designed with a size of <inline-formula> <tex-math notation="LaTeX">$38.2\times3.2$ </tex-math></inline-formula> mm<sup>2</sup>. No ground clearance is needed between the antenna and the chassis ground.

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