Difference between Active Tag and Passive Tag
While both the tags, i.e. Active RFID tags or Passive RFID tags use the energy embedded in radio frequency to communicate between tag and its reader, the method of powering the tags is different. Whereas the Active RFID possesses a battery (i.e. an internal power source) within itself to continuously power the tag and its RF communication circuitry, the Passive RFID tags have no battery. Their power source is reader, which sends out electromagnetic waves that induce a current in the tag's antenna. Thus, a Passive tag uses electromagnetic RF energy transferred from the reader to the tag as the power the tag. Hence, Passive RFID requires stronger signals from the reader. With some part of the energy already having been consumed in providing power to the tag, the signal strength returned from the tag is reduced to a low level.
A perfectly reverse process takes place in Active RFID. An Active RFID requires a low-level signal to be received by the tag as the tag does not require the reader to power the tag, and it further allows the tag to generate high-level signals to be sent back to the reader. The Active RFID tags have a transmitter and their own power source (typically a battery). The consumption of this power is targeted at disposing of two functions: to run the microchip's circuitry and, to broadcast a signal to a reader (this is the same way a cell phone transmits signals to its base station).
Hence, a passive tag is only powered when it comes within a reader filed. But an Active RFID tag gets continuously powered irrespective of its being in the reader field. This provides the Active tags two important functionary advantage over Passive tags. One, the Active tags can ‘beacon,’ or initiate communication with a reader or even other tags. And two, an active tag can contain external sensors to monitor other parameters like temperature, humidity, motion, and other conditions.
Now the question is regarding the applicability of Active and Passive tags. The Active tags are used with fixed RFID readers so that real-time asset monitoring at various points can be ensured, hence they are useful for tracking high-value goods when there is a requirement of such goods to be scanned over long ranges, such as railway wagons on a track. Obviously deployment of Active tags result in heavy costs than passive tags, which means it is never cost-effective to use them on low-cost items. Further, the Active tags provide a better layer of security than passive RFID.