A MIMO antenna design based on the characteristic mode

Abstract

In this article, multiple-input multiple-output (MIMO) antennas with high isolation and low correlation for LTE Band 8 (880-960 MHz) were designed by adopting a planar inverted-F antenna (PIFA) and a slot antenna. Based on characteristic mode theory, MIMO antennas utilize two different types of antennas to excite orthogonal modes for enhanced isolation and correlation. The proposed PIFA is designed to excite the ground mode along the length of the ground plane, and the slot antenna is proposed to adopt the ground mode along the width of the ground plane as a radiator; this provides greatly improved isolation and diversity performance compared to the reference MIMO antennas using two PIFAs. During simulation, the isolation is enhanced from below 4 to 20 dB. The measured envelope correlation coefficient (ECC) of the proposed MIMO antennas had an average value of 0.06, but the reference MIMO antennas had a very high ECC of 0.7.