Optimal Dual-Antenna Design in a Small Terminal Multiantenna System

This letter introduces a novel 2.6-GHz multiple-input-multiple-output (MIMO) antenna system for mobile terminals. The antenna structures consist of a broadband main antenna covering most of the LTE-A bands and a narrowband second antenna operating at the 2.6-GHz band. The main antenna is a traditional monopole-type capacitive coupling element (CCE) placed on the short edge of the terminal. The second antenna consists of two out-of-phase fed inductive coupling elements (ICEs) placed on the long edges of the chassis. The main purpose of the letter is to demonstrate that this kind of antenna system offers good performance in terms of electromagnetic (EM) isolation and envelope correlation between the antennas. This has been experimentally verified and is originated on the fact that both antennas excite effectively different orthogonal wavemodes, which is studied with the help of the theory of characteristic wavemodes.