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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 40.8 × 3 mm 2 . 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 38.2 × 3.2 mm 2 . No ground clearance is needed between the antenna and the chassis ground.
Deng et al. (Wed,) studied this question.