Signals received at base station antennas are typically elliptically polarized in a way more like vertical polarization than horizontal polarization. This creates a common problem with dual polarized base station antennas (like the first generation of Ubiquiti dual-polarity antennas) since the vertically polarized antenna element generally maintains a stronger receive signal than the horizontally polarized antenna element.
This can be overcome by slanting the orthogonal polarized antenna elements to +/- 45 degrees. By slanting one of the antenna elements 45 degrees to the left and the other 45 degrees to the right, improved equality in received signal levels can be achieved. This can help improve coverage in congested environments.
Another advantage to using these types of cross polarized antennas is in co-located wireless system installations. Since multiple antennas are used within the same facility or tower, this often creates interference issues among antennas which are usually vertically or horizontally polarized. Using 45 degree slanted cross polarized antennas on the client side as well on the base station side can greatly reduce interference and improve performance.
Ubiquiti’s AirFiber 5GHz Dish series uses 45-degree slant for improved noise immunity and Signal‑to‑Noise Ratio (SNR)
Author: George Hardesty