Spatial correlation in uniform circular arrays subject to mutual coupling

The diversity performance of the multi-antenna system depends heavily on the signal correlations between the different antenna elements. Strongly correlated antenna signals substantially reduce the diversity gain of the receiver. In absence of mutual coupling, the spatial correlation can be easily evaluated. In the presence of mutual coupling, however, the treatment becomes more involved and the complex pattern correlation differs substantially from the theoretical estimate of the envelope correlation, mainly because of the deformation of the antenna pattern due to mutual coupling. In new communication systems, based on adaptive and MIMO antennas, antenna correlation also has a major influence on the performance and mutual coupling is playing an important role.