An Emerging
Technology:
Radio
Frequency Identification
|
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