A compact pattern diversity MIMO antenna with enhanced bandwidth and high-isolation characteristics for WLAN/5G/WiFi applications

In this article, a novel multiple input multiple output (MIMO) antenna with compact structure and diverse radiation patterns is designed for a wireless communication device. Four monopole antenna elements are placed orthogonally at the corner of the substrate. A decoupling structure composed of a circular patch and 4 L-shaped branches placed counterclockwise is printed on the upper surface of the substrate to reduce coupling between antenna elements. Due to the surface current on the circular parasitic patch, which was acquired by coupling with the monopole antenna, the MIMO antenna exhibits an omnidirectional radiation pattern at low frequencies and a directional radiation pattern at high frequencies. In order to verify the accuracy of theoretical analysis and simulated results, the proposed antenna with a compact size of 30 mm x 30 mm is fabricated and measured. The measured results show that the overlapping bandwidths (S-11 <= -10 dB) are 28.8% from 4.58 to 6.12 GHz and over 4.02 dBi gain. Furthermore, the measured results of pattern diversity are basically consistent with the simulated results, and the measured isolation is up to 15.4 dB, which suggest that the presented antenna can be applied to WLAN/5G/WiFi wireless communication.