Compact UWB Uniplanar Four-Port MIMO Antenna Array With Rejecting Band

A compact uniplanar four-port multiple-input-multiple-output (MIMO) antenna array is presented. The antenna covers a small area of 38.3 × 38.3 mm
²
and is developed on a single layer of a laminate of ε
_r
= 4.5 and width 0.8 mm. The MIMO array has an impedance bandwidth of 3-13.2 GHz with an average gain of 4.1 dBi and efficiency between 72% and 97%. The main decoupling technique used in this MIMO array was polarization diversity. Additionally, a set of slits was etched in the ground plane to reduce the ECC to 0.02 and less in the operative bandwidth. A distinctive characteristic of the proposed array is that it is uniplanar and can be easily implemented in mobile terminals where the antennas are printed in only one face of a dielectric surface that is not completely flat.