On capacity and correlation of multi-antenna systems employing multiple polarizations

Wireless communications have experienced an explosive growth the last decades. So far, the main applications have been voice service and low rate data services such as short messaging. However, the next generation of communication systems aim at providing wireless Intemet and multimedia services that require high or very high data rates. A promising way of achieving these data rates is to use multiple antennas at both the transmitter and the receiver, i.e. MultiInput Multi-Output (MIMO) systems [2, 41. These systems typically employ arrays of spatially separated elements at both ends. However, more compact implementations are possible if the polarization properties of the antenna also are exploited. An interesting concept that exploits polarization was introduced in [l], where a sixfold increase in capacity over a single polarized antenna was reported. This dramatic capacity increase was obtained by exploiting the full ElectroMagnetic (EM) field instead of just a single field component. In [l] neither the impact of the radiation pattem of the antenna nor the angular spread of the multipath components were analyzed. This paper will study the performance of a system that employs a multi-element multi-polarized antenna consisting of three electric dipoles and three magnetic dipoles, that measures all six components of the EM field. The correlation and channel capacity of such a system will be analyzed for various angular spreads and the combined effects of the radiation pattems and the polarizations of the antennas will be discussed.