Systematic design of MIMO terminal antennas using theory of characteristic modes

The Theory of Characteristic Modes (TCM) offers a natural and systematic way to design Multiple-Input Multiple-Output (MIMO) antennas with high total efficiency and uncorrelated antenna patterns. In this paper, recent advances in the growing field of TCM-aided MIMO antenna design are reviewed. In particular, the focus is on the challenging problem of designing MIMO antennas for compact mobile terminals below 1 GHz. It was found that low correlation can be achieved by allowing only one antenna to excite the single-mode terminal chassis. However, this led to small bandwidths for other antennas. To improve the bandwidth performance, the chassis could be slightly modified to support multiple excitable modes, which can give larger bandwidths for the multi-antennas designed to couple into these modes.