RFID > RFID Tags > Passive

Passive tags, as their name implies, have no internal power, or if they do they do not use it in the transmitting of the signal. Passive tags are energised via the incoming Radio Frequency (RF) signal from the reader, which generates a small current in the antenna. This current activates the silicon chip in the circuit, effectively waking it up and thus enabling the RFID tag to send out a response to the reader. The aerial or antenna of passive tags is designed to both pick up and transmit an RF signal.

 

Since they do not require their own power source, passive tags are typically smaller than active tags and can come in a variety of different forms, such as self adhesive labels, laminated paper tickets, laminated plastic cards or enclosed in specialist housing for application on difficult surfaces such as metal. Passive tags can have read distances from 2mm (ISO 14443) to a few meters (ISO 18000-6) depending on the particular Radio Frequency used and the design of the antenna. Passive tags may also contain batteries, but these batteries are not for transmitting data but for retaining the memory of the tag. As passive tags do not generally have an internal source of power they are cheaper than Active tags.