Adaptive Quad-Element Multi-Wideband Antenna Array for User-Effective LTE MIMO Mobile Terminals

An LTE MIMO antenna array, which is adaptive to the effects of the user´s body, is presented for mobile terminals. The bands of 750-960 MHz and 1700-2700 MHz are covered with a good efficiency in free space. Three kinds of user effects are studied, namely, “SAM head and PDA hand,” “PDA hand,” and “dual hands.” The array is formed by selecting the best two elements out of four, with the two ports and grounding points of the other two elements open. The user effects on MIMO channel capacity are reduced through the adaptive selection of two optimal antenna elements. The total efficiency, envelope correlation coefficient, and multiplexing efficiency are presented for the three kinds of user effects. In the lower band, the decreased correlation due to the optimal selection improves the multiplexing efficiency. The underlying physical mechanisms and some general rules are discussed. The specific absorption rate (SAR) in the “SAM head and PDA hand” case is studied. Experiments for the three kinds of user effects are also carried out.