An eight-port antenna system for fifth-generation (5G) multi-input multi-output (MIMO) mobile communication in smartphones is proposed, working in 3.5 GHz frequency band (3400-3600 MHz) and 5 GHz frequency band (4800-5100 MHz). The presented eight-port antenna array consists of four vertical structure antennas placed at four corners and four horizontal structure antennas etched along the two long sides of the circuit board. The height of vertical structure is only 4 mm, which is suitable for ultra-thin smartphones. The design of eight-port antenna array was fabricated and measured. According to the test results, an ideal impedance matching (superior to 10 dB), preeminent isolation (superior to 17 dB) and excellent efficiency (superior to 61%) are obtained over the 3.5 GHz frequency band and 5 GHz frequency band. In order to evaluate MIMO performance, the ergodic channel capacities and envelope correlation coefﬁcients (ECC) are also investigated.
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