RFID- Radio Frequency Identification

RFID is one of the most popular method of short range wireless communications.

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Radio frequency identifi cation (RFID) is an automatic identifi cation method, relying
on storing and remotely retrieving data using devices called RFID tags or transponders.
An RFID tag is an object that can be attached to or incorporated into
a product, animal, or person for the purpose of identifi cation using radio waves.
Chip-based RFID tags contain silicon chips and antennas. Passive tags require no
internal power source, whereas active tags require a power source. RFID is also
called dedicated short range communication (DSRC).
In a typical RFID system, individual objects are equipped with a small, inexpensive
tag. The tag contains a transponder with a digital memory chip that is
given a unique electronic product code. The transponder emits messages with an
identifi cation number that is retrieved from a database and acted upon accordingly.
The writable memory is used to transmit information among RFID readers
in different locations The interrogator, an antenna packaged with a transceiver and decoder, emits
a signal activating the RFID tag so it can read and write data to it. 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. The application software on the
host processes the data, and may perform various fi ltering operations to reduce
the numerous often redundant reads of the same tag to a smaller and more useful
data set.
The following are the RFID components and their characteristics:
Tags
Active (with watch-sized battery)
Passive (without battery)
Semi-active (with battery)
Size (varies from less than 1 square inch to many square inches)
Dependent on power and frequency (13.56 MHz, 433 MHz, 900 MHz,
2.4 GHz with power from 1 mW to 1 W)
Memory can be read only, write one and read many with 1 byte to
512 Kilo-bytes storage.
Reader
Receive data
Validate data
Send data to tag
Middleware
Host data management software applications

The following are the key features of RFID:
No line-of-sight. RFID tags do not need to be visible to read or write.
Robust. Because RFID systems do not need to be visible, they can be encased
within rugged material protecting them from the environment in which they
are being used. This means they can be used in harsh fl uid and chemical
environments and rough handling situations.
Read speed. Tags can be read from signifi cant distances and can also be read
very quickly — for example, on a conveyor.

Reading multiple items. A number of tagged items can be read at the same
time within an RF fi eld. This cannot be done easily with visual identifi ers.
Security. Because tags can be enclosed, they are much more diffi cult to tamper
with. A number of tag types now also come programmed with a unique identifi er (serial identifi cation) which is guaranteed to be unique throughout
the world.

Programmability. Many tags are read/write capable, rather than read only.
This means that information can be written to the tag, perhaps to show
that the item being tagged has gone through a particular process, or that its
condition or status has changed somehow.

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