Correlation coefficient and loading effects for MIMO antennas in a reverberation chamber

We explore the effect of loading a reverberation chamber on the calculation of the correlation coefficient of two-element antenna arrays (similar to the type used in multiple-input multiple-output (MIMO) wireless devices). The changes in correlation coefficient with loading are compared to the changes in a squared, mismatch-corrected version of the transmission coefficient 〈|S_xy|²〉 as a function of chamber loading. The correlation coefficient and corresponding coefficient of variation were not significantly different for the unloaded versus loaded measurements as compared to the S parameter metric. The results presented here indicate that since the correlation coefficient is for the most part independent of loading, characterizing the spatial uniformity of the chamber would not be useful. On the other hand, loading a chamber in order to match a real-world environment will not affect the measured correlation between antennas, which is crucial in the performance evaluation of MIMO systems.