Integrated Inverted-F and Open-Slot Antennas in the Metal-Framed Smartphone for $2\times2$ LTE LB and $4\times4$ LTE M/HB MIMO Operations

Six antennas placed on the short edges of the metal-framed smartphone for the long-term evolution (LTE) multi-input multi-output (MIMO) operation are presented. The six-antenna structure comprises three antennas placed on the top edge of the smartphone and three antennas placed on the bottom edge thereof. The three antennas on the bottom edge are identical to those on the top edge. Each three-antenna structure consists of one inverted-F antenna (IFA) that covers the LTE low band (LB) in 698-960 MHz and two open-slot antennas (OSAs) that cover the LTE middle/high bands (M/HB) in 1710-2690 MHz. The three-antenna structure is compactly integrated, with the IFA placed between two OSAs, to fit in one short edge of the smartphone. In addition, the presence of the IFA is able to decrease the mutual coupling between two OSAs in the LTE M/HB. Furthermore, two IFAs at opposite short edges can also show good decoupling to have decreased envelope correlation coefficients in the LTE LB. The six antennas at two short edges can, therefore, achieve good performances for 2 × 2 LTE LB MIMO and 4 × 4 LTE M/HB MIMO operations.