A compact four-band high-isolation quad-port MIMO antenna for 5G and WLAN applications

Abstract

A miniaturized quad-port multiple-input-multiple-output (MIMO) antenna, generating four-band and high port isolation properties, is developed for 5G and wireless local area network (WLAN) applications. The realized MIMO antenna consists of four elements. Each element combines multiple L-shaped and rectangular branches with concave grounds, so that good impedance matching in four frequency bands is reached. The four elements are orthogonally placed to reduce current coupling. Moreover, four pairs of rotationally symmetrical strip lines are added to further improve the isolation between the units at low frequency. The antenna has been optimized to achieve a compact size of 39 mm × 39 mm × 1.6 mm, covering three 5G bands (2.6/3.5/4.8 GHz) and the 5.8 GHz WLAN band. In addition, inter-port isolation is better than 21.5 dB. Furthermore, the measured envelop correlation coefficient is smaller than 0.012 in the desired bands. Measurements also show that the radiation patterns and gains of the fabricated antenna agree well with the simulated ones. The diversity gain is as good as 9.94 dB. Moreover, the channel capacity loss is satisfactory, being below 0.4 bits/s/Hz. Satisfactory efficiency and diversity performance are realized. These facts indicate that the antenna system is a promising candidate for MIMO usage on 5G and WLAN devices.