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RFID - > What is RFID?
A basic RFID
system consists of three components:
An antenna or coil
A reader (tranceiver)
A transponder (RF tag) electronically programmed with unique
information
RFID
Frequency Ranges
The advantages
Future developments of RFID
The antenna
emits radio signals to activate the tag and read and write data to it.
Antennas are the conduits between the tag and the transceiver, which controls
the system's data acquisition and communication. Antennas are available in a
variety of shapes and sizes; they can be built into a door frame to receive
tag data from persons or things passing through the door, or mounted on an
interstate toll booth to monitor traffic passing by on a freeway. The
electromagnetic field produced by an antenna can be constantly present when
multiple tags are expected continually. If constant interrogation is not
required, the field can be activated by a sensor device.
Transceiver
(Reader)
Often the antenna is packaged with the transceiver and decoder to become a
reader (a.k.a. interrogator), which can be configured either as a handheld or
a fixed-mount device. The reader emits radio waves in ranges of anywhere from
one inch to 100 feet or more, depending upon its power output and the radio
frequency used. 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.
Tags
RFID tags come in a wide variety of shapes and sizes. Paper-thin tags, pasted
onto books and files, can be hidden between pages. Tags can be screw-shaped to
identify trees or wooden items, or credit-card shaped for use in access
applications. The anti-theft hard plastic tags attached to merchandise in stores
are RFID tags. In addition, heavy-duty 5- by 4- by 2-inch rectangular
transponders used to track intermodal containers or heavy machinery, trucks, and
railroad cars for maintenance and tracking applications are RFID tags.
RFID tags are
categorized as either active or passive. Active RFID tags are powered by an
internal battery and are typically read/write, i.e., tag data can be rewritten
and/or modified. An active tag's memory size varies according to application
requirements; some systems operate with up to 1MB of memory. In a typical
read/write RFID work-in-process system, a tag might give a machine a set of
instructions, and the machine would then report its performance to the tag. This
encoded data would then become part of the tagged part's history. The
battery-supplied power of an active tag generally gives it a longer read range.
The trade off is greater size, greater cost, and a limited operational life
(which may yield a maximum of 10 years, depending upon operating temperatures
and battery type).
Passive RFID tags
operate without a separate external power source and obtain operating power
generated from the reader. Passive tags are consequently much lighter than
active tags, less expensive, and offer a virtually unlimited operational
lifetime. The trade off is that they have shorter read ranges than active tags
and require a higher-powered reader. Read-only tags are typically passive and
are programmed with a unique set of data (usually 32 to 128 bits) that cannot be
modified. Read-only tags most often operate as a license plate into a database,
in the same way as linear barcodes reference a database containing modifiable
product-specific information.
Frequency
Ranges
RFID systems are also distinguished by their frequency ranges. Low-frequency (30
KHz to 500 KHz) systems have short reading ranges and lower system costs. They
are most commonly used in security access, asset tracking, and animal
identification applications. High-frequency (850 MHz to 950 MHz and 2.4 GHz to
2.5 GHz) systems, offering long read ranges (greater than 90 feet) and high
reading speeds, are used for such applications as railroad car tracking and
automated toll collection. However, the higher performance of high-frequency
RFID systems incurs higher system costs.
Advantages
The significant advantage of all types of RFID systems is the noncontact,
non-line-of-sight nature of the technology. Tags can be read through a variety
of substances such as snow, fog, ice, paint, crusted grime, and other visually
and environmentally challenging conditions, where barcodes or other optically
read technologies would be useless. RFID tags can also be read in challenging
circumstances at remarkable speeds, in most cases responding in less than 100
milliseconds. The read/write capability of an active RFID system is also a
significant advantage in interactive applications such as work-in-process or
maintenance tracking. Though it is a costlier technology (compared with
barcode), RFID has become indispensable for a wide range of automated data
collection and identification applications that would not be possible otherwise.
Developments
Developments in RFID technology continue to yield larger memory capacities,
wider reading ranges, and faster processing. It is highly unlikely that the
technology will ultimately replace barcode - even with the inevitable reduction
in raw materials coupled with economies of scale, the integrated circuit in an
RF tag will never be as cost-effective as a barcode label. However, RFID will
continue to grow in its established niches where barcode or other optical
technologies are not effective. If some standards commonality is achieved -
whereby RFID equipment from different manufacturers can be used interchangeably
- the market will very likely to grow exponentially.
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