RFID tag can be grouped into passive, semi-passive and active.

• Passive Tag
  Tags that are energized by readers electromagnetic field.
  They are low cost & small size because no batteries are needed.
  Passive tags are classified into 3 types:-

  • Class 0:- are read only tags with simple 1D number. The id is typically a manufacture programmed 64 or 96 bit number which can be EPC & cannot be modified.
  • Class 1:- are read/write passive tags that can be written once, either by the manufacture or the user.
  • Class 2:- are read/write passive tags that can be written several times and has additional features like data logging, cryptography may be included
    
    

• Semi - Passive Tag
  Semi - Passive tags generally use energy from batteries to work in addition to radio frequency transmission as passive tags.

  • Class 3:- with extra energy the tags can increase their reading distance range as well as providing new functionalities eg:- Sensor.

• Active Tag
  Active tags provided with batteries allowing the tag generate its own radio frequency signal.
  They might also include additional feature like sensors, encryptions & data processing among other functionalities.
  • Class 4 :- Provide communication functionalities with other active tags &have the same features as class 3.
  • Class 5:- have reader capabilities enabling them to communicate with all types of tags.