Radio Frequency Identification
( RFID ) is an automatic identification
method, relying on storing and remotely retrieving data using devices
called RFID tags or transponders . An RFID tag is a small object that
can be attached to or incorporated into a product, animal, or person.
RFID tags contain silicon chips and antennas to enable them to receive
and respond to radio -frequency queries from an RFID transceiver .
Passive tags require no internal power source, whereas active tags
require a power source. Typical RFID tags usually can not store more
than 2KB of data [22], limiting the amount of information that they can
send.
The range of RFID tags range from just a few millimeters to
several
meters using passive tags (tags without their own energy source), to
100 meters or more with active tags (tags that are powered by an energy
source). The range also depends on other factors, like the RFID reader
used and interference. The transfer rate is also highly varying,
depending on the implementation, frequency used, whether active tags or
passive tags are used, and possibly other factors.
Types of RFID Tags:
RFID tags can be either passive ,
semi-passive (also known as semi-active
), or active .
-
Passive: Passive
RFID tags have no internal power supply. The minute electrical current
induced in the antenna by the incoming radio frequency signal provides
just enough power for the CMOS integrated circuit (IC) in the tag to
power up and transmit a response. Most passive tags signal by
backscattering the carrier signal from the reader. This means that the
aerial (antenna) has to be designed to both collect power from the
incoming signal and also to transmit the outbound backscatter signal.
The response of a passive RFID tag is not just an ID number (GUID): tag
chip can contain nonvolatile EEPROM(Electrically Erasable Programmable
Read-Only Memory) for storing data. Lack of an onboard power supply
means that the device can be quite small: commercially available
products exist that can be embedded under the skin.
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Semi-passive: Semi-passive
RFID tags are very similar to passive tags except for the addition of a
small battery. This battery allows the tag IC to be constantly powered.
This removes the need for the aerial to be designed to collect power
from the incoming signal. Aerials can therefore be optimized for the
backscattering signal. Semi-passive RFID tags are faster in response
and therefore stronger in reading ratio compared to passive tags.
-
Active: Unlike
passive and semi-passive RFID tags, active RFID tags (also known as beacons
) have their own internal power source which
is used to power any ICs and generate the outgoing signal. They are
often called beacons because they broadcast their own signal. They may
have longer range and larger memories than passive tags, as well as the
ability to store additional information sent by the transceiver. To
economize power consumption, many beacon concepts operate at fixed
intervals. At present, the smallest active tags are about the size of a
coin. Many active tags have practical ranges of tens of meters, and a
battery life of up to 10 years.
Some applications of RFID are:
RFID References:
RFID
Journal
RFID
News
WikiPedia RFID
What is RFID
Sun Java and RFID
RFID Tutorial
RFID
Beginners Guide
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