An Emerging Technology:
Radio Frequency Identification

Home History Technology Basics RFID Use in Libraries Advantages and Disadvantages Future Vendors For More Information


Technology Basics

A RFID system is composed of an item with a tag, a reader to read data from the tag, and a server or docking station with software that interfaces with a system that makes use of the information from the tag. A tag is constructed of a silicon microchip and is etched with an antenna.

RFID Tags

Depending on the type of tag, it can operate either actively or passively. An active tag sends radio signals out until picked up by the reader. A passive tag waits for a reader to send radio waves, and then reflects these waves back to the reader. A passive tag has no energy supply of its own, and therefore does not have the ability to generate radio waves, which are, fundamentally, energy. Active tags have an energy source and can generate radio waves to transmit the data stored on the chip. There are two types of active tags, transponders which are awoken by a reader, and beacons which emit their radio waves at preset intervals. Passive tags are less inexpensive and smaller than active tags. Active tags tend to be used in commercial applications such as large-asset cargo tracking or tollbooth collection. Passive tags tend to be used for individual item identification.

Active RFID tags can operate at 455MHz, 2.45MHz, or 5.8GHz. Because of these very high frequencies, the tags can be read by readers at distances of 60 – 300ft. These characteristics make active tags useful in large warehouses, factories, and shipping terminals. Additionally, active RFID tags tend to store a lot of information on the chips, including a record of items in the cargo and a date, time, location stamp of readers it has communicated with, and even an on board temperature sensor. Depending on the memory and the durability of the housing for the tag, active tags cost between $10 and $50.
Passive tags can transmit on low, high, or ultrahigh frequencies. Passive tags used in libraries tend to operate at the high, 13.56 MHz, frequency and therefore the distance that these tags can communicate with the reader is limited to a few inches to a few feet, which is what is needed in a library setting. These tags cost from $0.20 to $0.85.
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RFID readers

The second part of an RFID system is the reader, or sensor. Readers and tags operate on the same frequency, as determined by the manufacturer. The reader’s antenna emits an electromagnetic field and the tag is able to pick up this field and draw energy from it. The tag uses this energy to run the circuits on the chip. In doing so, the electric load on the tag’s antenna changes. It is the function of the reader’s antenna to detect these changes and convert them to binary information. This binary information is sent to the third part of the RFID system, the server. It is with the software on the server that the unique identification information held on the tag becomes of any value. The server uses this identification number to track the item, or record the items movements.

RFID relies on radio waves and therefore these waves are subject to interference just as any other radio waves. Distance is most likely the greatest factor affect the performance of RFID equipment. The distance the radio waves can travel before degrading is directly related to their initial energy. Since passive tags reflect the radio waves emitted by the reader, the signal is weaker in the direction from the tag to the antenna than it is from the antenna to the tag. To retain the greatest accuracy of data transfer, it is important to remain well within the vendor’s guidelines, usually about three feet. If stronger waves are used initially, it is possible that the waves will bounce off surfaces and read unintended items. Radio waves are blocked by metals, such as aluminum, and the waves can not be read through water. Electromagnetic noise from machines, older LAN’s, cordless phones, and wireless computer terminals may also affect the reliability of the signal between the reader and the tag.
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Commercial Applications of RFID

In the 1990’s the Auto-ID center at the Massachusetts Institute of Technology (MIT) developed the technologies that allowed the price of an individual tag to decrease. This was mainly due to the idea that the tag only needed to store an individual code, and that the useful information was tied to this code, but stored on a computer. Additionally the Auto-ID center developed the Electronic Product Code that gives a unique number to each item, an air interface protocol, and a network structure that stores information. In addition to the Department of Defense, large commercial organizations such as Wal-Mart, Target, the grocery stores Albertson’s and Kroger have either begun to use, or plan to use RFID to control their supply chain at every level. This includes RFID tagging at the manufacture level, these tags are read when the items enter a warehouse, when they are shipped to stores, and when they arrive in stores. RFID tags will also be used in the stores to determine when items should be placed on the shelves. When the supply is getting low, communication, that starts with the RFID tags can be sent back up the supply chain. These large organizations have helped the cost of RFID to decrease while increasing the public awareness of the technology.

RFID is being used in the manufacturing of automobiles and airplanes to track the completion and location of different components. RFID tags have been used for a few years by some buildings for keyless entry. Gas stations and toll collection booths are other familiar commercial applications. The use of RFID is expanding. Tags and readers are being used to monitor prisoners in Texas, Michigan, California, and Illinois, and school children in New York. A hospital in the Bronx embeds RFID tags in the bracelets that patients wear, while other hospitals apply RFID tags to infants. RFID tags are also used in sports, including timing chips for marathon runners, and there are tags used in some soccer balls to determine if the ball crosses the plane into the goal. Tickets for the 2008 Olympic games will have RFID tags in them. Gamblers in some Las Vegas casinos use RFID embedded chips that are meant to combat counterfeit chips. Attendees at the Nashville Sounds minor league baseball games can use an RFID embedded wristband to purchase their concessions. The commercial applications of RFID tags seem limited only by the imagination and not the innovation of the technology.
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Created by Sally Egloff for LBSC 690 Information Technology at University of Maryland