Correlation between the output signals from a dual polarized antenna

Dual polarized antennas are traditionally characterized in terms of a port-to-port isolation co-polar and cross-polar patterns. We identify the critical parameter when the antenna is used as as sensor in a polarization diversity reception system. This turns out to be the far-field coupling between the two channels, the inverse of which characterizes the orthogonality of the channels. We derive an expression for the power correlation between the outputs of a dual polarized antenna when used in different environments. The expression is used to analyze two ideal antenna types: a dual polarized aperture coupled patch element and a pair of orthogonal slanted dipoles, both over an infinite ground plane. Both antennas have /spl plusmn/45/spl deg/ linear polarizations, which is preferable since they provide identical azimuth patterns and equal mean power. We show that under Gaussian assumptions about the incident fields, the far-field coupling provides valuable insight to the correlation between the output signals from the two channels of a dual polarized antenna.