EM waves usually travel in two main modes i.e Linearly Polarized (Vertical or Horizontal) or Circularly Polarized (RHCP or LHCP). When EM waves propagate in a single plane either horizontal or vertical, it is called as linear propagation. And when EM waves propagate in a manner where the amplitude of the waves are constant but they rotate with time, it is called circular polarization.

Antenna polarization is very important when it comes to RFID. The reader sends out EM waves via an RFID antenna to the RFID Tag. Each polarization has advantages and disadvantages which can be seen in the table below.