Evaluating MIMO systems with multi-polarized antennas.

It is well known that spatially separated antennas can provide uncorrelated signals in a rich scattering environment. Under suitable conditions, orthogonally polarized antennas can provide uncorrelated signals without requiring any or much spatial separation. The channel capacity gains that result from MIMO (in general) depend heavily on the scattering environment. In this paper, we are interested in studying the capacity gains (or losses) that result from using co-located multi-polarized antennas in relation to that which would result from using an antenna array with spatially separated antennas. These gains are likely a function of the scattering environment and propagation conditions. To facilitate this study, we utilize a physical model for MIMO wireless channels, which takes into account scatterer geometry, gain and polarization pattern of the antenna and polarization coupling mechanism, among other details. The channel capacity performance of three different 3 times 3 MIMO configurations are reported for various different channel scenarios. The results indicate that a multi-polarized tripole antenna configuration provides robust MIMO performance for all the channel scenarios considered. A multimode patch antenna configuration also displays robust performance and also has the added advantage of being co-planar.