Radio-frequency identification (RFID) is the use of an object (typically referred to as an RFID tag) applied to or incorporated into a product, animal, or person for the purpose of identification and tracking using radio waves. Some tags can be read from several meters away and beyond the line of sight of the reader.

In 1946 Léon Theremin invented an espionage tool for the Soviet Union which retransmitted incident radio waves with 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 passive covert listening device, not an identification tag, it is considered to be a predecessor of RFID technology. The technology used in RFID has been around since the early 1920s according to one source (although the same source states that RFID systems have been around just since the late 1960s).[1][dead link][2][3][4]

Similar technology, such as the IFF transponder invented in the United Kingdom in 1939, was routinely used by the allies in World War II to identify aircraft as friend or foe. Transponders are still used by most powered aircrafts to this day.

 

consisted of a transponder with 16 bit memory for use as a toll device. The basic Cardullo patent covers the use of RF, sound and light as transmission media. The original business plan presented to investors in 1969 showed uses in transportation (automotive vehicle identification, automatic toll system, electronic license plate, electronic manifest, vehicle routing, vehicle performance monitoring), banking (electronic check book, electronic credit card), security (personnel identification, automatic gates, surveillance) and medical (identification, patient history).

A very early demonstration of reflected power (modulated backscatter) RFID tags, both passive and semi-passive, was performed by Steven Depp, Alfred Koelle, and Robert Freyman at the Los Alamos National Laboratory in 1973[2]. The portable system operated at 915 MHz and used 12-bit tags. This technique is used by the majority of today's UHFID and microwave RFID tags.

The first patent to be associated with the abbreviation RFID was granted to Charles Walton in 1983 U.S. Patent 4,384,288.

Types

RFID are broadly classified as active and passive. The active one contains battery on the tag while the passive tags do not contain any battery. There are additionally other class of RFIDs such as chipless RFID, the RFID tags that do not contain any chip on the tag, and also RFID sensor tags, which incorporate sensors on the tag. [5]

Miniaturization

RFIDs can be highly miniaturised, which makes it easy to conceal or incorporate them in other items. For example, in 2009 researchers at Bristol University successfully glued RFIDs to live ants in order to study their behavior.[6] This trend towards increasingly miniaturized RFIDs is likely to continue as technology advances.

Hitachi holds the record for smallest RFID powder at 0.05mm x 0.05mm. The powder type tags are 64 times smaller than the new RFID tags.[7] manufacture enabled by using the Silicon-on-Insulator (SOI) process manufacturing. These "dust" sized chips can store 38-digit numbers using 128-bit Read Only Memory (ROM). [8]. A major challenge is the attachment of the antennas.

Potential alternatives to the radio frequencies (0.125–0.1342, 0.140–0.1485, 13.56, and 868–928 MHz) used are seen in optical RFID (or OPID) at 333 THz (900 nm), 380 THz (788 nm), 750 THz (400 nm). [9]. The awkward antennae of RFID can be replaced with photovoltaic components and IR-LEDs on the ICs.

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