The RFID reader antenna sends and receives signals, and has both electrical and magnetic characteristics; when radio waves propagate in space, the direction of the electric field changes according to a certain rule. This phenomenon is called radio wave polarization. According to different polarization modes, it can be divided into the following two types of RFID antennas:

1、Linear polarization antenna: 

The signal propagation direction (vertical or horizontal) in which electromagnetic waves propagate completely on a plane. When the direction of the tag is known and fixed, the polarization of the RFID antenna and the RFID tag match (vertical corresponds to vertical or horizontal corresponds to horizontal) ), the best read rate can be obtained at this time.

2、Circularly polarized antenna: 

When the angle between the polarization plane of the electric wave and the normal plane of the earth changes periodically from 0-360°, that is, the electric field changes in size and the direction changes with time. The trajectory at the end of the electric field vector is perpendicular to the direction of propagation. When the projection on the plane is a circle, it is circular polarization.