Small array antenna for 2x2 MIMO terminal using folded loop antenna

Recently, MIMO technologies for mobile phones have been investigated to achieve high-speed data communication. It is preferable to have a smaller and more efficient antenna system for the MIMO terminal. Although built-in antennas are more convenient, coupling between antennas and the human body is larger than with extended antennas. So far, for the built-in elements, we have proposed a folded loop antenna (FLA) with balanced feed and a parallel plane antenna (PPA) with unbalanced feed. Because of the smaller human effects, these antennas may work effectively as MIMO antenna arrays. In this paper, 3 types of 2times2 MIMO antenna are investigated to show the effectiveness of the built-in antenna array for the terminal in a multi-pass wave environment. The channel capacity is employed to estimate the antenna performance.