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.
2. WRC-15 Press Release, (Nov. 27, 2015), , World Radiocommunication Conference Allocates Spectrum for Future Innovation, [Online], Avail-able: http://www.itu.int/net/pressoffice/press releases/2015/56.aspx.
3. Li, Y.-X., C.-Y.-D. Sim, Y. Luo, and G.-L. Yang, "Multiband 10-antenna array for sub-6 GHz MIMO applications in 5-G smartphones," MIMO applications in 5-G smartphones, Vol. 6, 28041-28053, May 2018.
4. Wong, K.-L. and J. Y. Lu, "3.6-GHz 10-antenna array for MIMO operation in the smartphone," Microw. Opt. Technol. Lett., Vol. 57, No. 7, 1699-1704, Jul. 2015. doi:10.1002/mop.29181
5. Wong, K.-L., J.-Y. Lu, L.-Y. Chen, W.-Y. Li, and Y.-L. Ban, "8-antennaand 16-antenna arrays using the quad-antenna linear array as a building block for the 3.5-GHz LTE MIMO operation in the smartphone," Microw. Opt. Technol. Lett., Vol. 58, No. 1, 174-181, Jan. 2016. doi:10.1002/mop.29527
6. Ban, Y.-L., C. Li, and C.-Y.-D. Sim, "4G/5G multiple antennas for future multi-mode smartphone applications," IEEE Access., Vol. 4, 2981-2988, Jun. 2016. doi:10.1109/ACCESS.2016.2582786
7. Qin, Z., W. Geyi, M. Zhang, and J. Wang, "Printed eight-element MIMO system for compact and thin 5G mobile handest," Electron. Lett., Vol. 52, No. 6, 416-418, 2016. doi:10.1049/el.2015.3960
8. Ban, Y.-L., C. Li, C.-Y.-D. Sim, G. Wu, and K.-L. Wong, "4G/5G multiple antennas for future multi-mode smartphone applications," IEEE Access, Vol. 4, 2981-2988, 2016. doi:10.1109/ACCESS.2016.2582786
9. Neto, A., D. Cavallo, G. Gerini, and G. Toso, "Scanning performances of wide band connected arrays in the presence of a backing reflector," IEEE Trans. Antenna Propag., Vol. 57, No. 10, 3092-3102, Oct. 2009. doi:10.1109/TAP.2009.2028631
10. Cavallo, D., A. Neto, G. Gerini, A. Micco, and V. Galdi, "A 3 to 5 GHz wideband array of connected dipoles with low cross polarization and wide-scan capability," IEEE Trans. Antennas Propag., Vol. 61, No. 3, 1148-1154, Mar. 2013. doi:10.1109/TAP.2012.2231920
11. Sharawi, M. S., M. Ikram, and A. Shamim, "A two concentric slot loop based connected array mimo antenna system for 4G/5G terminals," IEEE Trans. Antennas Propag., Vol. 65, No. 12, 6679-6686, Dec. 2017. doi:10.1109/TAP.2017.2671028
12. Guo, J.-L., L. Cui, C. Li, and B.-H. Sun, "Side-edge frame printed eight-port dual-band antenna array for 5G smartphone applications," IEEE Trans. Antennas Propag., Vol. 66, No. 12, 7412-7417, Dec. 2018. doi:10.1109/TAP.2018.2872130
13. Wong, K.-L. and C.-Y. Tsai, "Half-loop frame antenna for the LTE metalcasing tablet device," IEEE Trans. Antennas Propag., Vol. 65, No. 1, 71-81, Jan. 2017. doi:10.1109/TAP.2016.2630716
14. Yuan, B., Y. Cao, G. Wang, and B. Cui, "Slot antenna for metal-rimmed mobile handsets," IEEE Antennas Wireless Propag. Lett., Vol. 11, 1334-1337, Nov. 2012.
15. Zhao, A.-P. and Z.-Y. Ren, "Size reduction of self-isolated MIMO antenna system for 5G mobile phone applications," IEEE Trans. Antennas Propag. Lett., Vol. 18, No. 1, 152-156, Nov. 2018. doi:10.1109/LAWP.2018.2883428
16. Aziz, R. S., A. K. Arya, and S.-O. Park, "Multiband full-metal-rimmed antenna design for smartphones," IEEE Antennas Wireless Propag. Lett., Vol. 15, 1987-1990, Mar. 2016. doi:10.1109/LAWP.2016.2548018
17. Chen, Q.-G., J.-P. Wang, L. Ge, Y.-J. Li, T.-Q. Pei, and C.-Y.-D. Sim, "Single ring slot based antennas for metal-rimmed 4G/5G smartphones," IEEE Trans. Antennas Propag., Vol. 67, No. 3, 1476-1478, Mar. 2019. doi:10.1109/TAP.2018.2883686
18. Wang, S., S. Member, and Z. Du, "Decoupled dual-antenna system using crossed neutralization lines for LTE/WWAN smartphone applications," IEEE Antennas Wireless Propag. Lett., Vol. 14, 523-526, Nov. 2015.
19. Yang, Y., Q. Chu, and C. Mao, "Multiband MIMO antenna for GSM, DCS, and LTE indoor applications," IEEE Trans. Antennas Propag. Lett., Vol. 15, 1573-1576, Jan. 2013.
20. Sharawi, M. S., "Printed multi-band MIMO antenna systems and their performance metrics," IEEE Antennas and Propag. Magazine, Vol. 55, No. 5, 218-232, Oct. 2013. doi:10.1109/MAP.2013.6735522