RF ID


RF ID



What is RFID:


RFID stands for Radio-Frequency IDentification. The acronym refers to small electronic devices that consist of a
small chip and an antenna. The chip typically is capable of carrying 2,000 bytes of data or less.


The RFID device serves the same purpose as a bar code or a magnetic strip on the back of a credit card or ATM
card; it provides a unique identifier for that object. And, just as a bar code or magnetic strip must be scanned to
get the information, the RFID device must be scanned to retrieve the identifying information.

RFID Works Better Than Barcodes


A significant advantage of RFID devices over the others mentioned above is that the RFID device does not need
to be positioned precisely relative to the scanner. We’re all familiar with the difficulty that store checkout clerks
sometimes have in making sure that a barcode can be read. And obviously, credit cards and ATM cards must be
swiped through a special reader.


In contrast, RFID devices will work within a few feet (up to 20 feet for high-frequency devices) of the scanner. For
example, you could just put all of your groceries or purchases in a bag, and set the bag on the scanner. It would be
able to query all of the RFID devices and total your purchase immediately.


RFID technology has been available for more than fifty years. It has only been recently that the ability to
manufacture the RFID devices has fallen to the point where they can be used as a "throwaway" inventory or
control device. Alien Technologies recently sold 500 million RFID tags to Gillette at a cost of about ten
cents per tag.


One reason that it has taken so long for RFID to come into common use is the lack of standards in the industry.
Most companies invested in RFID technology only use the tags to track items within their control; many of the
benefits of RFID come when items are tracked from company to company or from country to country.



Common Problems with RFID


Some common problems with RFID are reader collision and tag collision. Reader collision occurs when the signals
from two or more readers overlap. The tag is unable to respond to simultaneous queries. Systems must be
carefully set up to avoid this problem. Tag collision occurs when many tags are present in a small
area; but since
the read time is very fast, it is easier for vendors to develop systems that ensure that tags respond one at a time.

 
How does RFID work?


A Radio-Frequency Identification system has three parts:

A scanning antenna

A transceiver with a decoder to interpret the data

A transponder – the RFID tag – that has been programmed with information.


The scanning antenna puts out radio-frequency signals in a relatively short range. The RF radiation
does two things:

It provides a means of communicating with the transponder (the RFID tag) AND

It provides the RFID tag with the energy to communicate (in the case of passive RFID tags).

This is an absolutely key part of the technology; RFID tags do not need to contain batteries, and can therefore
remain usable for very long periods of time (maybe decades).

The scanning antennas can be permanently affixed to a surface; handheld antennas are also available. They can
take whatever shape you need; for example, you could build them into a door frame to accept data from persons or
objects passing through.

When an RFID tag passes through the field of the scanning antenna, it detects the activation signal from the
antenna. That "wakes up" the RFID chip, and it transmits the information on its microchip to be picked up by the
scanning antenna.

In addition, the RFID tag may be of one of two types. Active RFID tags have their own power source; the
advantage of these tags is that the reader can be much farther away and still get the signal. Even though some of
these devices are built to have up to a 10 year life span, they have limited life spans. Passive RFID tags,
however, do not require batteries, and can be much smaller and have a virtually unlimited life span.

RFID tags can be read in a wide variety of circumstances, where barcodes or other optically read technologies are
useless.

The tag need not be on the surface of the object (and is therefore not subject to wear)

The read time is typically less than 100 milliseconds

Large numbers of tags can be read at once rather than item by item.

 


The Difference between RFID and Barcode technology:

RFID tags and barcodes both carry information about products. However, there are important differences between
these two technologies:

Barcode readers require a direct line of sight to the printed barcode; RFID readers do not require a direct line of
sight to either active RFID tags or passive RFID tags.

RFID tags can be read at much greater distances; an RFID reader can pull information from a tag at distances up to
300 feet. The range to read a barcode is much less, typically no more than fifteen feet.

RFID readers can interrogate, or read, RFID tags much faster; read rates of forty or more tags per second are
possible. Reading barcodes is much more time-consuming; due to the fact that a direct line of sight is required, if
the items are not properly oriented to the reader it may take seconds to read an individual tag. Barcode readers
usually take a half-second or more to successfully complete a read.

Line of sight requirements also limit the ruggedness of barcodes as well as the reusability of barcodes. (Since line
of sight is required for barcodes, the printed barcode must be exposed on the outside of the product, where it is
subject to greater wear and tear.) RFID tags are typically more rugged, since the electronic components are better
protected in a plastic cover. RFID tags can also be implanted within the product itself, guaranteeing greater
ruggedness and reusability.

Barcodes have no read/write capability; that is, you cannot add to the information written on a printed barcode.
RFID tags, however, can be read/write devices; the RFID reader can communicate with the tag, and alter as
much of the information as the tag design will allow.

RFID tags are typically more expensive than barcodes, in some cases, much more so.