Network theory analysis of coupled antenna diversity performance

In antenna diversity systems, mutual coupling impacts the element terminal impedance and radiation pattern characteristics, leading to altered diversity performance. Most studies of this effect only include the effect of the coupling on the pattern. In this paper, we present a framework based on network theory that incorporates the impact of antenna termination in assessing the diversity performance of coupled systems. A scattering parameter (S-parameter) representation is used as the analysis framework for mutually-coupled antenna networks. The performance of antenna diversity systems depends upon the signal strength on each antenna branch, as well as the signal correlation between branches. We use the covariance matrix for the voltages received on each branch to assess these metrics. The Hermitian match is an optimal match for power transfer, and can be chosen to diagonalize the covariance matrix.