RFID
TECHNOLOGY
Radio Frequency Identification (RFID) is a form of contactless
automatic identification and data capture (AIDC) technology and was
developed in the 1980's for tracking and access applications. Effective
in manufacturing and other hostile environments where barcode labels
can not survive, RFID has established itself in a wide range of markets
including automated vehicle identification (AVI) and cargo
identification because of its ability to track moving objects.
How does it work?
In an RFID system, data is carried in a tag or smart label and
retrieved by machine-readable means. A basic RFID system consists of
three components: an antenna or coil, a coupler or reader and a tag
that is electronically programmed with fixed (read only) or variable
(read/write) data. The reader activates the tag by sending a radio
signal with a preset frequency. Data stored in the tag is then decoded
by the reader and transmitted to a host computer to be processed.
RFID Tags
RFID Tags are either active or passive. Active tags are powered by an
internal battery and are typically read/write devices. Hence, they have
high power-to-weight ratio, greater read range, finite lifetime,
greater size and greater cost compared with passive tags. Passive tags
derive the power to operate from the field generated by the reader.
They are much lighter than active tags, less expensive, offer a
virtually unlimited operational lifetime, shorter read ranges and
require a higher-powered reader. RFID Tags come in a wide variety of
physical shapes, sizes and can be further processed in a variety of
protective housings (i.e. converted into paper labels and injected in
plastic molds).
Antennas
Antennas emit radio signals to activate the tags and read and write
data to them. Antennas are the conduits between the tags and the
couplers, which control the system's data acquisition and
communication. Antennas have the ability to produce an electromagnetic
field at a constant pace to read tags in a continuous mode. When
packaged with a coupler, the combination becomes a reader, configured
either as a hand-held or a fixed-mount device. Radio waves are emitted
in ranges of anywhere from one inch to one hundred feet or more,
depending upon the power output and frequency used.
Wireless Communication
Communication of data between tags and readers is by wireless
communication. Two methods distinguish and categorize RFID systems; one
based upon close-proximity electromagnetic (or inductive) coupling and
one based upon propagating electromagnetic waves. Three frequency
ranges are generally distinguished for passive RFID systems; low,
intermediate (medium) and high.
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