Radio-Frequency Identifier

Radio Frequency Identifer


Radio-frequency identification (RFID) uses electromagnetic fields to automatically identify and track tags attached to objects. The tags contain electronically stored information. Unlike a barcode, the tags don't need to be within the line of sight of the reader, so it may be embedded in the tracked object. RFID is one method of automatic identification and data capture (AIDC).

Since RFID tags can be attached to cash, clothing, and possessions, or implanted in animals and people, the possibility of reading personally-linked information without consent has raised serious privacy concerns.

Short History

In 1945, Léon Theremin invented a listening device for the Soviet Union which retransmitted incident radio waves with the added audio information. Sound waves vibrated a diaphragm which slightly altered the shape of the resonator, which modulated the reflected radio frequency. Even though this device was a covert listening device, rather than an identification tag, it is considered to be a predecessor of RFID because it was passive, being energized and activated by waves from an outside source.


RFID tags are easy to conceal or incorporate in other items. For example, in 2009 researchers at Bristol University successfully glued RFID micro-transponders to live ants in order to study their behavior. This trend towards increasingly miniaturized RFIDs is likely to continue as technology advances.

Hitachi holds the record for the smallest RFID chip, at 0.05 mm × 0.05 mm. This is 1/64th the size of the previous record holder, the mu-chip. Manufacture is enabled by using the silicon-on-insulator (SOI) process. These dust-sized chips can store 38-digit numbers using 128-bit Read Only Memory (ROM). A major challenge is the attachment of antennas, thus limiting read range to only millimeters.

Human Implantation

A surgeon implants British scientist Dr Mark Gasson in his left hand with an RFID microchip (March 16, 2009)

Biocompatible microchip implants that utilize RFID technology are being routinely implanted in humans. The first reported experiment with RFID implants was conducted by British professor of cybernetics Kevin Warwick who had an RFID chip implanted in his arm by his general practitioner George Boulos in 1998. In 2004 the 'Baja Beach Clubs' operated by Conrad Chase in Barcelona and Rotterdam offered implanted chips to identify their VIP customers, who could in turn use it to pay for service. In 2009 British scientist Mark Gasson had an advanced glass capsule RFID device surgically implanted into his left hand and subsequently demonstrated how a computer virus could wirelessly infect his implant and then be transmitted on to other systems.

The Food and Drug Administration in the United States approved the use of RFID chips in humans in 2004.

There is controversy regarding human applications of implantable RFID technology including concerns that individuals could potentially be tracked by carrying an identifier unique to them. Privacy advocates have protested implantable RFID chips, warning of potential abuse. Some are concerned this could lead to abuse by an authoritarian government, to removal of freedoms, and to the emergence of an "ultimate panopticon", a society where all citizens behave in a socially accepted manner because others might be watching.

On July 22, 2006, Reuters reported that two hackers, Newitz and Westhues, at a conference in New York City demonstrated that they could clone the RFID signal from a human implanted RFID chip, indicating that the device was not as secure as was previously claimed.

Power Source: Passive RFID vs Active RFID

In general, three main parts make up in a passive RFID system – an RFID reader or interrogator, an RFID antenna, and RFID tags. Unlike active RFID tags, passive RFID tags only have two main components – the tag’s antenna and the microchip or integrated circuit (IC).

Passive RFID systems use tags with no internal power source and instead are powered by the electromagnetic signal transmitted from an RFID reader. The reader sends energy to an antenna which converts that energy into an RF wave that is sent into the read zone. Once the tag is read within the read zone, the RFID tag’s internal antenna draws in energy from the RF waves. The energy moves from the tag’s antenna to the IC and powers the chip which generates a signal back to the RF system. This is called backscatter. The backscatter, or change in the electromagnetic or RF wave, is detected by the reader (via the antenna), which interprets the information.

Active RFID systems use battery-powered RFID tags that continuously broadcast their own signal.


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