Trade-Off Between Optimal Efficiency and Envelope Correlation Coefficient of MIMO Antenna Clusters

The presented article proposes a theory for the optimization of multiple-input-multiple-output antenna performance by assessing feeding coefficients. Antenna clusters with multiple feeding ports are utilized, which brings additional degrees of freedom and improves the performance. This work considers fixed shape and matching networks. The method is based on quadratic programming and maximizes total efficiency constrained by channel correlation and channel power distribution. The formulation provided in the article enables establishing trade-offs between all mentioned metrics. Evaluating the performance in this manner provides comprehensive information about the chosen geometry and port placement. Selected examples demonstrate how efficiency and channel correlation can be both in agreement but also in significant conflict. The effect of frequency dispersion on feeding is also investigated.