Polarization diversity gain and base station antenna characteristics

Dual polarized antennas are traditionally characterized in terms of port-to-port isolation and co- and cross-polar radiation patterns. In this paper we instead identify the critical parameter when the antenna is used as a sensor in a polarization diversity reception system. This turns out to be the far-field coupling between the two channels. We calculate the antenna output power correlation and diversity gain, using maximum ratio combining, under Rayleigh fading conditions. Two different antennas are compared: a dual polarized aperture coupled patch 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 cases.