Parasitically Isolated 4-element MIMO Antenna for 5G/WLAN Applications

This communication analyses the influence of parasitic structure on the performance of a four-element multiple-input multiple-output antenna. A simple square-shaped patch antenna with a circular slot is designed to operate from 4.5 to 5.8 GHz. It is duplicated orthogonally to form a four-element MIMO antenna, and it is built on an FR4 substrate of size 30 × 30 × 0.8 mm³. This 4-element MIMO is operating from 3.4 to 6.3 GHz having wider bandwidth than a single element. The minimum isolation observed between all the elements is 15 dB. To improve the isolation parameter, a parasitic structure made of a rectangular window carrying 4 circular patches is proposed. The addition of parasitic structure perturbs the current distribution and reduces the mutual coupling between the adjacent and opposite radiators. The minimum isolation observed is 20 dB, and the maximum is 45 dB in the presence of a parasitic element. The proposed antenna is fabricated to verify the simulated results, and they are reasonably agreeing with simulation results. The proposed antenna shows good radiation and MIMO performance such as a peak gain of 4 dBi, the maximum radiation efficiency of 96%, and an envelope correlation coefficient of 0.001. The antenna is suitable for applications such as WiMAX (3.5/5.5 GHz), WLAN (5.2/5.8 GHz), and 5G Wi-Fi (6 GHz).