The polarization is a radiation feature for indicating the vector special direction of field strength of electromagnetic wave. If unspecified, the spatial direction of electric field vector usually serves as the polarization direction of electromagnetic wave. The spatial direction of electric field vector is the direction of maximum radiation by antenna.
The electromagnetic wave of which the spatial direction of electric filed vector keeps fixed any time is the linear polarization wave. With the ground as a reference, the polarization of which the direction of electric field vector is parallel to ground is the horizontal polarization wave and polarization of which the direction of electric field vector is vertical to ground is the horizontal polarization wave.
The spatial direction of electric field vector is not always fixed.
- If the endpoint trace of electric field vector forms a circle, the polarization wave is circular polarization wave.
- If the endpoint trace of electric field vector forms an ellipse, the polarization wave is elliptical polarization wave.
The elliptical polarization wave and circular polarization wave have polarization direction.
The electromagnetic wave of different bands caters for different polarization modes for propagation. The mobile communication systems usually choose vertical polarization while the broadcasting systems usually choose horizontal polarization. The elliptical polarization usually applies for satellite communication.
The polarization modes of antennas include the polarization and dual polarization, and they are all linear polarization. The dual polarization antenna reduces the impact from multi-path attenuation and improves the quality of signals received by the eNodeB by using polarization diversity. The dual polarization antenna in LTE networks usually use ±45° cross polarization mode.