A Multiband Multiple-input Multiple-output Antenna System for Long Term Evolution and Wireless Local Area Networks Handsets

Abstract

A novel multiband multiple-input-multiple-output (MIMO) antenna system is proposed. The MIMO antenna system consists of two antenna elements, each of which comprises of three radiators: a driven monopole, an S-shaped strip and an inverted F-shaped strip and occupies footprint of 15x18.5x0.8 mm3 only. The driven monopole acts as a quarter-wave monopole and stimulate higher mode resonance. The two strips are excited by electromagnetic coupling from the driven monopole and serve as two additional monopoles leading to a wideband performance for the lower band. The bandwidths (VSWR ≤ 2.75) achieved for the antenna element are 1.67 – 2.2 GHz for the lower band and 2.28 –2.95 GHz for the upper band which cover LTE-1, LTE- 2, LTE- 3, LTE- 7, LTE- 40 and WLAN 2.4 GHz bands. A T-shaped slot and another two slots are introduced to reduce the coupling effect between the two multiband antenna elements. The isolation achieved is higher than 18 dB over the whole band, leading to an envelope correlation coefficient of less than 0.01. Furthermore, the diversity characteristics of mean effective gains (MEGs) and diversity gain (DG) are also studied. Both the simulated and measured results are shown to illustrate the performance of the proposed multiband MIMO antenna system, and that confirms the suitability for LTE and WLAN handset applications.