A multiband dual-standard MIMO antenna system based on monopoles (4G) and connected slots (5G) for future smart phones

In this work, a 4G/5G multiple-input multiple-output (MIMO) antenna system is presented for smart phone applications. The 4G antenna operates from 1900 to 3212MHz and 3517 to 3712MHz with 1312 (69%) and 195 (5.5%) MHz measured bandwidths, respectively. The 5G antenna covers 25.7-30.50GHz band with 4.8GHz (18.7%) measured bandwidth. The 4G MIMO antenna system is based on 4-element wideband monopoles, while the 5G one is based on 2-element linear connected arrays (LCA). Four slots are etched to improve the isolation between the 4G MIMO antenna elements and then a 4x1 power divider/combiner is used to excite two of these slots to act as a LCA at mm-waves. The concept of dual function ground slots is very useful to implement 4G and 5G MIMO antenna systems on the single substrate. The proposed design is fabricated on RO4350B substrate with a height of 0.76mm and dielectric constant of 3.5. The overall size of the substrate is 115x65x0.76mm(3). The integrated wideband 4G/5G antenna system is a compact, low profile, and suitable for future smart phone applications. Isolation obtained was at least 15dB and the envelope correlation coefficient (ECC) values did not exceed 0.16 between all elements.