Four-Element Planar MIMO Antenna for Indoor Communications with High Isolation

A low-profile monopole microstrip antennas with multiple-input-multiple-output (MIMO) configuration for a 4G/5G communication terminal is presented. The MIMO antenna system consists of four elements that operate in the LTE1800/2600 and GSM1800 bands. The antenna elements are mounted along the four sides of a rectangular ground plane of size 120 x100 mm(2). Spatial diversity technique and a modified ground plane are used to enhance isolation between elements. To mitigate the mutual coupling effect, the lower corners of the ground plane have been truncated. The measured isolation is lower than -17 dB between any two elements over the operating frequency bands. The total efficiency ranges from 69% to 83% and from 73% to 86% over LTE1800 and LTE2600 bands, respectively. The diversity performance of the measured envelope correlation coefficient (ECC) and radiation patterns meet the diversity criteria for 4/5G networks.