Mutual Coupling and Correlation as Performance Metrics in Evaluating Multi-antenna Systems

We investigate the effectiveness of designing a multi-antenna system based on reducing the amount of mutual coupling between the antennas and the envelope correlation for spatial multiplexing systems. The investigation is carried out at 1880 MHz for a 2x2 multi-antenna system of vertically polarized dipole antennas. The effectiveness of the coupling and the correlation performance metrics were studied in three different propagation environments representing rural, sub-urban and urban channels. For completeness, other performance metrics of the channel power, the channel capacity, the antenna efficiency, and the imbalance between the antennas were also investigated. It was found that, except for a rural environment, the mutual coupling and the correlation represent incomplete information and optimizing the multi-antenna system based on these does not necessarily guarantee the best possible system performance. On the other hand, optimizing for the channel power and/or capacity would better represent the system performance.