On the available diversity gain from different dual-polarized antennas

Dual-polarized antennas are traditionally characterized in terms of port-to -port isolation and co- and cross-polar radiation patterns. For base statio n antennas in a mobile communications system, the critical parameter is ins tead the far-held coupling between the two channels. In a mobile communicat ion system, base station antennas with a nominal +/- 45 degrees to vertical linear polarization are commonly used. Such antennas are difficult to desi gn with constant polarization characteristics in azimuth. We calculate the antenna output power correlation and diversity gain under Rayleigh fading c onditions and different values of the environment cross-polar discriminatio n. Two different antennas are compared: a dual-polarized aperture coupled p atch and a slanted dipole configuration, both over an infinite groundplane. We show that the aperture coupled patch provides lower output correlation and higher diversity gain than the slanted dipoles in all investigated case s.