Compact 4 port MIMO antenna using polarization and pattern diversity

A compact 4 port MIMO antenna system is proposed in this paper with an area of 60×60 mm². The antenna operates at 2.45 GHz with an overall area of nearly 1λ. The antenna consists of a cross patch embedded inside a square ring patch antenna. The strong mutual coupling between ports is reduced below -24 dB by etching a square ring defected ground structure on the ground. The isolation structure reduces surface waves and cross polarization levels providing an isolation improvement of 8.5 dB. The antenna can be used for multiple input multiple output systems and have very low envelope correlation less than 0.1 between its waveforms. Measurements and characteristics of antenna system fabricated on an FR4 substrate are provided.