History of RFID tags
In 1945 Léon Theremin invented an espionage tool for
the Soviet government. Even though this device was a passive
covert listening device, not an identification tag, it has
been attributed the first known device and a predecessor to
RFID technology. The technology used in RFID has been around
since the early 1920s according to one source (although the
same source states that RFID systems have been around
just since the late 1960s).
A similar technology, the IFF transponder, was invented by
the British in 1939, and was routinely used by the allies in
World War II to identify airplanes as friend
or foe.
Another early work exploring RFID is the landmark 1948 paper
by Harry Stockman, titled "Communication by Means of Reflected
Power" (Proceedings of the IRE, pp 1196-1204, October
1948). Stockman predicted that "...considerable research
and development work has to be done before the remaining basic
problems in reflected-power communication are solved, and before
the field of useful applications is explored." It required
thirty years of advances in many different fields before RFID
became a reality.
Types of RFID tags
RFID tags can be active, semi-passive (=semi-active)
or 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 non-volatile 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. As of 2006, the smallest such devices measured
0.15 mm × 0.15 mm, and are thinner than a sheet of paper
(7.5 microns); such devices are practically invisible. Passive
tags have practical read distances ranging from about 2 mm
(ISO 14443) up to about few metres (ISO 18000-6) depending
on the chosen radio frequency. Due to their simplicity in design
they are also suitable for manufacture with a printing process
for the antennae. A development target is polycarbon semiconductor
tags to become entirely printed. Passive RFID tags do not require
batteries, and can be much smaller and have an unlimited life
span.
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 optimised for the backscattering
signal. Semi-passive RFID tags are faster in response and therefore
stronger in reading ratio compared to passive tags.
Active RFID tags or beacons, on the other hand, have their
own internal power source that is used to power any ICs and
generate the outgoing 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 metres,
and a battery life of up to 10 years.
Because passive tags are cheaper to manufacture and have no
battery, the majority of RFID tags in existence are of the
passive variety. As of 2006, these tags cost an average of
Euro 0.20 ($0.24 USD) at high volumes. Today, as universal
RFID tagging of individual products become commercially viable
at very large volumes, the lowest cost tags available on the
market are as low as 7.2 cents each in volumes of 10 million
units or more. Current demand for RFID integrated circuit chips
is expected to grow rapidly based on these prices.
The RFID system
An RFID system may consist of several components: tags, tag
readers, edge servers, middleware, and application software.
The purpose of an RFID system is to enable data to be transmitted
by a mobile device, called a tag, which is read by an RFID
reader and processed according to the needs of a particular
application. The data transmitted by the tag may provide identification
or location information, or specifics about the product tagged,
such as price, colour, date of purchase, etc. The use of RFID
in tracking and access applications first appeared during the
1980s. RFID quickly gained attention because of its ability
to track moving objects. As the technology is refined, more
pervasive and possibly invasive uses for RFID tags are in the
works.
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 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, often
employing Physical Markup Language (PML).
Take the example of books in a library. Security gates can
detect whether or not a book has been properly checked out
of the library. When users return items, the security bit is
re-set and the item record in the integrated library system
is automatically updated. In some RFID solutions a return receipt
can be generated. At this point, materials can be roughly sorted
into bins by the return equipment. Inventory wands provide
a finer detail of sorting. This tool can be used to put books
into shelf-ready order.
Regulation and standardization
There is no global public body that governs the frequencies
used for RFID. In principle, every country can set its own
rules for this. The main bodies governing frequency allocation
for RFID are:
- USA: FCC (Federal Communications Commission)
- Canada: DOC (Department of Communication)
- Europe: ERO, CEPT, ETSI, and national administrations (note
that the national administrations must ratify the usage of
a specific frequency before it can be used in that country)
- Japan: MPHPT (Ministry of Public Management, Home Affairs,
Post and Telecommunication)
- China: Ministry of Information Industry
- Australia: Australian Communication Authority.
- New Zealand: Ministry of Economic Development
Low-frequency (LF: 125 - 134.2 kHz and 140 - 148.5 kHz) and
high-frequency (HF: 13.56 MHz) RFID tags can be used globally
without a license. Ultra-high-frequency (UHF: 868 MHz-928 MHz)
cannot be used globally as there is no single global standard.
In North America, UHF can be used unlicensed for 908 - 928
MHz, but restrictions exist for transmission power. In Europe,
UHF is under consideration for 865.6 - 867.6 MHz. Its usage
is currently unlicensed for 869.40 - 869.65 MHz only, but restrictions
exist for transmission power. The North American UHF standard
is not accepted in France as it interferes with its military
bands. For China and Japan, there is no regulation for the
use of UHF. Each application for UHF in these countries needs
a site license, which needs to be applied for at the local
authorities, and can be revoked. For Australia and New Zealand,
918 - 926 MHz are unlicensed, but restrictions exist for transmission
power.
These frequencies are known as the ISM bands (Industrial Medical
Scientific). The return signal of the tag may still cause interference
for other radio users.
Additional regulations exist regarding health and environmental
issues.. For example, in Europe, the Waste Electrical and Electronic
Equipment Directive does not allow for RFID tags to be thrown
away. This means that RFID tags in cardboard boxes must be
removed before disposing of them. This is important because
RFID tags disrupt recycling. Health regulations exist as well;
see EMF (Electromagnetic field).
Some standards that have been made regarding RFID technology
include:
- ISO 11784 & 11785 - These standards regulate the Radio
frequency identification of animals in regards to Code Structure
and Technical concept
- ISO 14223/1 - Radio frequency identification of Animals,
advanced transponders - Air interface
- ISO 10536
- ISO 14443
- ISO 15693
- ISO 18000
- EPCglobal - this is the standardization framework that
is most likely to undergo International Standardisation according
to ISO rules as with all sound standards in the world, unless
residing with limited scope, as customs regulations, air-traffic
regulations and others. Currently the big distributors and
governmental customers are pushing EPC heavily as a standard
well accepted in their community, but not yet regarded as
for salvation to the rest of the world.
From http://en.wikipedia.org/wiki/Rfid |
