History of RFID tags

Some people think that the first known device may have been invented by Leon Theremin as an espionage tool for the Russian Government in 1945.

Perhaps the first work exploring RFID is the landmark 1948 paper by Harry Stockman, entitled "Communication by Means of Reflected Power" (Proceedings of the IRE, pp1196-1204, 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." It required thirty years of advances in many different fields before RFID became a reality.

Types of RFID tags

RFID tags can be either active or passive.

Passive RFID tags do not have their own power supply: the minute electrical current induced in the antenna by the incoming radio-frequency scan provides enough power for the tag to send a response. Due to power and cost concerns, the response of a passive RFID tag is necessarily brief: typically just an ID number (GUID). Lack of its own power supply makes the device quite small: commercially available products exist that can be embedded under the skin. As of 2004, the smallest such devices commercially available measured 0.4 mm ¡Á 0.4 mm, and thinner than a sheet of paper; such devices are practically invisible. Passive tags have practical read ranges that vary from about 10 mm up to about 6 metres.

Active RFID tags, on the other hand, must have a power source, and may have longer ranges and larger memories than passive tags, as well as the ability to store additional information sent by the transceiver. At present, the smallest active tags are about the size of a coin. Many active tags have practical ranges of tens of metres, and a battery life of up to several years.

As passive tags are much cheaper to manufacture and do not depend on a battery, the vast majority of RFID tags in existence are of the passive variety. As of 2004 tags cost from US$0.40. The aim is to produce tags for less than US$0.05 to make widespread RFID tagging commercially viable. However, chip manufacturers' supply of integrated circuits is not sufficient and demand is too low for prices to come down soon. Analysts from independent research companies like Gartner and Forrester Research agree that a price level of less than $0.10 is only achievable in 6-8 years, a potential hurdle to widespread passive RFID adoption. However, using some new manufacture techniques can lower the price of RFID at a fast pace.

While the cost advantages of passive tags over active tags are significant, other factors including accuracy and reliability make the use of active tags very common today.

There are four different kinds of tags commonly in use. They are categorized by their radio frequency: low frequency tags (between 125 to 134 kilohertz), high frequency tags (13.56 megahertz), UHF tags (868 to 956 megahertz), and microwave tags (2.45 gigahertz). UHF tags cannot be used globally as there aren't any global regulations for their usage.

There are some transponder devices and contactless chip cards which deliver a similar function.