Large Screen Enabled Tri-port MIMO Handset Antenna for Low LTE Bands

In recent years, the screen-to-body ratio of mobile handsets has been increasing. Today, the screen nearly fills up the entire front side. Conventionally, the screen is mainly seen as a metallic object that adversely affects antenna performance. In this paper, the large screen is used for the first time to facilitate an additional uncorrelated MIMO port in a tri-port design, for several LTE bands below 1 GHz. To this end, the design procedure explicitly considers the screen together with the terminal chassis, which can be simply modelled as two metal plates. In particular, characteristic mode analysis of the double-plate model enables a sufficient number of resonant modes to be created, tuned and selectively excited to yield three uncorrelated MIMO ports in the low band. Simulation and measurement results are found to be in good agreement. The measured bandwidths of the three ports are 23%, 17% and 21%, respectively. Within the operating band, the measured isolation is above 13 dB, envelope correlation coefficient below 0.16 and average total efficiency above 72%.