RFID FAQ

History of RFID tags

An RFID tag used for electronic toll collection In 1945 Léon Theremin invented an espionage tool for the Soviet government which retransmitted incident radio waves with audio information. Even though this device was a passive covert listening device , not an identification tag, it has been attributed as the first known device and a predecessor to 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 ) .

A more similar technology, the IFF transponder, was invented by the British in 1939, and was routinely used by the allies in World War II to identify airplanes as friend or foe.

Another early work exploring RFID is the landmark 1948 paper by Harry Stockman, titled "Communication by Means of Reflected Power" (Proceedings of the IRE, pp 1196–1204, October 1948 ). Stockman predicted that "...considerable research and development work has to be done before the remaining basic problems in reflected-power communication are solved, and before the field of useful applications is explored."

Mario Cardullo claims that his U.S. Patent 3,713,148 in 1973 was the first true ancestor of modern RFID; a passive radio transponder with memory. The first demonstration of today's reflected power (backscatter) RFID tags was done at the Los Alamos Scientific Laboratory in 1973.

Types of RFID tags

RFID cards are also known as "proximity" or "proxy" cards and come in three general varieties: passive , semi-passive (also known as semi-active ), or active .

Passive

Passive RFID tags have no internal power supply. The minute electrical current induced in the antenna by the incoming radio frequency signal provides just enough power for the CMOS integrated circuit (IC) in the tag to power up and transmit a response. Most passive tags signal by backscattering the carrier signal from the reader. This means that the aerial (antenna) has to be designed to both collect power from the incoming signal and also to transmit the outbound backscatter signal. The response of a passive RFID tag is not just an ID number (GUID); the tag chip can contain nonvolatile EEPROM for storing data. Lack of an onboard power supply means that the device can be quite small: commercially available products exist that can be embedded under the skin. As of 2006 , the smallest such devices measured 0.15 mm × 0.15 mm, and are thinner than a sheet of paper (7.5 micrometers ). [4] The lowest cost EPC RFID tags which is the chosen standard by Wal-Mart , DOD , Target , Tesco in the UK and Metro AG in Germany are available today at a price of 5 Cent each. The addition of the antenna creates a tag that varies from the size of postage stamp to the size of a post card. Passive tags have practical read distances ranging from about 10 cm (4 in.) ( ISO 14443 ) up to a few meters ( EPC and ISO 18000-6 ) depending on the chosen radio frequency and antenna design/size. Due to their simplicity in design they are also suitable for manufacture with a printing process for the antennas. Passive RFID tags do not require batteries, can be much smaller, and have an unlimited life span. Non-silicon tags made from polymer semiconductors are currently being developed by several companies globally. Simple laboratory printed polymer tags operating at 13.56 MHz were demonstrated in 2005 by both PolyIC (Germany) and Philips (The Netherlands). If successfully commercialized, polymer tags will be roll printable, like a magazine, and much less expensive than silicon-based tags. The end game for most item level tagging over the next few decades is that RFID tags will be wholly printed - the same way a barcode is today - and be virtually free, like a barcode.

Semi-passive

Semi-passive RFID tags are very similar to passive tags except for the addition of a small battery. This battery allows the tag IC to be constantly powered, which removes the need for the aerial to be designed to collect power from the incoming signal. Aerials can therefore be optimized for the backscattering signal. Semi-passive RFID tags are thus faster in response, though less reliable and powerful than active tags. Semi-passive tags offer benefits in environments where there is a lot of metal or fluids, which typically scatter the RF field and can cause non-reads with passive tags. As semi-passive tags are pre-energized, they can be read more reliably in these more difficult environments.

Active

Unlike passive RFID tags, active RFID tags have their own internal power source which is used to power any ICs that generate the outgoing signal. Active tags are typically much more reliable (e.g. fewer errors) than passive tags due to the ability for active tags to conduct a "session" with a reader. Active tags, due to their onboard power supply, also transmit at higher power levels than passive tags, allowing them to be more effective in "RF challenged" environments like water (including humans/cattle, which are mostly water), metal (shipping containers, vehicles), or at longer distances. Many active tags have practical ranges of hundreds of meters, and a battery life of up to 10 years. Some active RFID tags include sensors such as temperature logging which have been used in concrete maturity monitoring or to monitor the temperature of perishable goods. Other sensors that have been married with active RFID include humidity, shock/vibration, light, radiation, temperature and atmospherics like ethylene. Active tags typically have much longer range (approximately 300 feet) and larger memories than passive tags, as well as the ability to store additional information sent by the transceiver. The United States Department of Defense has successfully used active tags to reduce logistics costs and improve supply chain visibility for more than 15 years. At present, the smallest active tags are about the size of a coin and sell for a few dollars.