Millimeter-wave antennas are the trend nowadays because of the necessity of higher data rates. Designing a supplementary efficient antenna capable of dealing with dual bands has several challenges. This chapter reports the problematic approaches introduced in the field of a millimeter wave design. Prevailing investigations in millimeter-waves and MIMO antennas have a tendency to emphasize discovering how to increase the data rate without the need of increasing the bandwidth and what type of antenna preferred in the 5G band. However, there is a little indication that researchers have come close to the issue of antenna integration in the mobile handset with the intent of adding multiple antennas with multi-band capability in a small space. Accordingly, the target of this chapter is to offer a summary of how the small-dimensional MIMO antennas with band duality for 5G mobile communications can be intended, designed, sustained and fabricated.
