Radio frequency identification ( RFID ) is a method of remotely storing and retrieving data using devices called RFID tags . An RFID tag is a small object, such as an adhesive sticker, that can be attached to or incorporated into a product. RFID tags contain antennas to enable them to receive and respond to radio -frequency queries from an RFID transceiver.
History of RFID tags
Although 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, the first real usage of RFID devices predates that. During World War II the United Kingdom used RFID devices to distinguish returning British airplanes from inbound German ones. At first, RADAR was only able to signal the presence of a plane, not the kind of plane it was. Later, Identification friend or foe (IFF) transponders carried in friendly aircraft gave them a distinctive "blip" on radar screens.
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 × 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 5 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.
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.
Today, there are 4 major frequency ranges that RFID systems operate at. As a rule of thumb, low-frequency systems are distinguished by short reading ranges, slow read speeds, and lower cost. Higher-frequency RFID systems are used where longer read ranges and fast reading speeds are required, such as for vehicle tracking and automated toll collection. Microwave requires the use of active RFID tags.
125 - 148 KHz
||Pet and ranch animal identification;
||library book identification;
clothing identification; smart cards
||Supply chain tracking:
Box, pallet, container, trailer tracking
||Highway toll collection;
vehicle fleet identification
*Tag costs are estimates and should only be used as a reference.
The RFID System
An RFID system may consist of several components: tags, tag readers, tag programming stations, circulation readers, sorting equipment, and tag inventory wands. Security can be handled in two ways. Security gates can query the ILS to determine its security status or the tag may contain a security bit which would be turned on and off by circulation or self-check reader stations.
The purpose of an RFID system is to enable data to be transmitted by a portable device, called a tag, which is read by an RFID reader and processed according to the needs of a particular application. The data transmitted by the tag may provide identification or location information, or specifics about the product tagged, such as price, color, date of purchase, etc. The use of RFID in tracking and access applications first appeared during the 1980s. RFID quickly gained attention because of its ability to track moving objects. As the technology is refined, more pervasive—and invasive—uses for RFID tags are in the works.
In a typical RFID system, individual objects are equipped with a small, inexpensive tag. The tag contains a transponder with a digital memory chip that is given a unique electronic product code. The interrogator, an antenna packaged with a transceiver and decoder, emits a signal activating the RFID tag so it can read and write data to it. When an RFID tag passes through the electromagnetic zone, it detects the reader's activation signal. The reader decodes the data encoded in the tag's integrated circuit (silicon chip) and the data is passed to the host computer for processing.
Take the example of books in a library. Security gates can detect whether or not a book has been properly checked out of the library. When users return items, the security bit is re-set and the item record in the ILS is automatically updated. In some RFID solutions a return receipt can be generated. At this point, materials can be roughly sorted into bins by the return equipment. Inventory wands provide a finer detail of sorting. This tool can be used to put books into shelf-ready order.
RFID and DoD Policy
The US Department of Defense has issued a series of RFID policy guidelines that state the requirements for its suppliers to meet.
Passive RFID tags are required for all DoD contracts issued on or after Oct 1, 2004, for delivery of materials on or after Jan 1, 2005. Passive tags need to be applied to all freight/cargo containers, cases, pallets and to individual "high-value" items that require the military's UID (Unique Identification Code). Containers shipped outside the continental US need to have active tags with content and point of origin information.
Beginning in 2006 and 2007, there are additional RFID tagging requirements.