Polarized multi-antenna systems are an effective solution for reducing inter-antenna spacing while still maintaining low inter-antenna correlation. Traditionally, only dual-polarized antenna systems are used for polarized transceivers. In this paper, tri-polarized antenna systems are investigated. Starting from the polarization mechanisms in the wireless propagation channel, it is shown that dual-polarized MIMO systems show high sensitivity to the transmitter and receiver orientation, which may be very critical in practical applications. Tri-polarized MIMO systems are introduced as a solution to obtain a robust MIMO performances, which are independent of the transmitter and receiver orientation. The performances of dual- and tri-polarized MIMO systems are evaluated on real-world measured channels, and the limits of each of these systems is highlighted.
Quitin, F., Oestges, C., Panahandeh, A., Horlin, F., & De Doncker, P. (2012). Tri-polarized MIMO systems in real-world channels: Channel investigation and performance analysis. Physical Communication, 5(4), 308-316. https://doi.org/10.1016/j.phycom.2012.04.004 (Original work published 2012)