RFID tags and NFC transponders are short range RF communications devices. Radio frequency identification (RFID) tags are used in applications including public transport ticketing, security authentication, livestock tracking, animal identification, warehouse stock tracking and anti-theft retail tagging. Near field communication (NFC) devices are used in applications including smartphone information exchange, ticket reading, access control, wireless payment, smartcards, identity and security access.

 

RFID tags are available in passive, active or battery-assisted-active types. Active tags have an onboard battery that continually periodically transmits its ID. Battery assisted tags detect the presence of an RFID reader and enable the battery to transmit ID data. Passive tags utilize the RF energy from the RFID reader using electromagnetic induction to transmit data. Passive tags are short range devices with a maximum range 30 cm under ideal situations but typically 10 cm in practice. Special RFID tags and readers are available to extend this range to 1-2 m. Active tags can communicate over hundreds of meters.

 

NFC transponders are intended to fulfill the role of both tag and reader. They operate over short distances of approximately 10 cm for secure contactless information exchange. Transponders fulfill the role of initiator or target in the communications link. The initiator actively generates an RF field that can power a passive target through electromagnetic induction. This allows NFC initiators to be able to read passive RFID devices. A target NFC device can cause operation in passive or active modes. In passive mode, the initiator provides power to the target with its RF field. It is in this mode that the passive target is operating as a transponder. In active mode both initiator and target are self-powered half duplex transceivers alternating transmit and receive modes for two way communications. Devices encode and transmit data at different rates when in passive or active modes.

Near field devices operate at a 13.56 MHz frequency, whereas RFID can operate in three frequency ranges. This includes 125-134 kHz low frequency, 13.56 MHz high frequency and 856-960 MHz ultra high frequency. Several billion RFID tags are sold globally every year. It is predicted that up to 250 billion RFID tags will be sold annually by 2021.