Glossary of RFID Terms
An RFID tag that comes with a battery that
is used to power the microchip's circuitry and transmit a signal to a reader. Active
tags can be read from 100 feet or more away, but they're expensive - more than $20
each. They're used for tracking expensive items over long ranges. For instance,
the US military uses active tags to track containers of supplies arriving in ports.
Amplitude The maximum absolute value of a periodic curve measured
along its vertical axis (the height of a wave, in layman's terms).
Antenna: The antenna is the conductive element that enables the tag to send
and receive data. Passive tags usually have a coiled antenna that couples with the
coiled antenna of the reader to form a magnetic field. The tag draws power from
Anti-collision: A general term used to cover methods of preventing radio
waves from one device from interfering with radio waves from another. Anti-collision
algorithms are also used to read more than one tag in the same reader's field.
Auto-ID Center : A non-profit collaboration
between private companies and academia that is pioneering the development of an
Internet-like infrastructure for tracking goods globally through the use of RFID
Automatic Identification: Sometimes called automatic data capture. These
are methods of collecting data and entering it directly into computer systems without
human involvement. Technologies normally considered part of auto-id include bar
codes, biometrics, RFID and voice recognition.
Back scatter: A method of communication between tags and readers. RFID tags
using back-scatter technology reflect back to the reader a portion of the radio
waves that reach them. The reflected signal is modulated to transmit data. Tags
using back scatter technology can be either passive or active, but either way, they
are more expensive than tags that use inductive coupling.
Bar code: A standard method of identifying the manufacturer and product category
of a particular item. The barcode was adopted in the 1970s because the bars were
easier for machines to read than optical characters. Barcodes' main drawbacks are
they don't identify unique items and scanners have to have line of sight to read
Contactless smart card:
An awkward name for a credit
card or loyalty card that contains an RFID chip to transmit information to a reader
without having to be swiped through a reader. Such cards can speed checkout, providing
consumers with more convenience.
Chipless RFID tag:
An RFID tag that doesn't depend on an integrate microchip.
Instead, the tag uses materials that reflect back a portion of the radio waves beamed
at them. A computer takes a snapshot of the waves beamed back and uses it like a
fingerprint to identify the object with the tag. Companies are experimenting with
embedding RF reflecting fibers in paper to prevent unauthorized photocopying of
certain documents. But chip less tags are not useful in the supply chain, because
even though they are inexpensive, they can't communicate a unique serial number
that can be stored in a database.
RFID tracking systems set up within a company. Since
the tracked item never leaves the company's control, it does not need to worry about
using technology based on open standards.
See inductive coupling
Die: The silicon block onto which circuits have been etched.
EEPROM (Electrically Erasable Programmable Read-Only Memory):
A non-volatile storage device on microchips. Usually bytes can be erased and
reprogrammed individually. RFID tags that use EEPROM are more expensive than factory
programmed tags, but they offer more flexibility because the end user can write
an ID number to the tag at the time the tag is going to be used.
Electromagnetic compatibility (EMC): The ability of a system or product to
function properly in environment where other electromagnetic devices are used and
not be a source itself of electromagnetic interference.
Electromagnetic interference (EMI): Interference caused when the radio waves
of one device distort the waves of another. Cells phones, wireless computers and
even robots in factories can produce radio waves that interfere with RFID tags.
Electronic article surveillance (EAS): Simple electronic tags that can be
turned on or off. When an item is purchased (or borrowed from a library), the tag
is turned off. When someone passes a gate area holding an item with a tag that hasn't
been turned off, an alarm sounds. EAS tags are embedded in the packaging of most
Electronic Product Code: (EPC): A 96-bit code, created
by the Auto-ID Center, that will one day replace barcodes. The EPC has digits to
identify the manufacturer, product category and the individual item. It is backed
by the United Code Council and EAN International, the two main bodies that oversee
Error correcting code: A code stored on an RFID tag to enable the reader
to figure out the value of missing or garbled bits of data. It's needed because
a reader might misinterpret some data from the tag and think a Rolex watch is actually
a pair of socks.
Error correcting mode: A mode of data transmission between the tag and reader
in which errors or missing data is automatically corrected.
Error correcting protocol: A set of rules used by readers to interpret data
correctly from the tag.
European Article Numbering (EAN): The bar code standard used throughout Europe,
Asia and South America. It is administered by EAN International.
Excite: The reader is said to "excite" a passive tag when the reader
transmits RF energy to wake up the tag and enable it to transmit back.
eXtensible markup language (XML): A widely
accepted way of sharing information over the Internet in a way that computers can
use, regardless of their operating system
Factory programming: Some read-only have to have their identification
number written into the silicon microchip at the time the chip is made. The process
of writing the number into the chip is called factory programming.
Field programming: Tags that use EEPROM, or non-volatile memory, can be programmed
after it is shipped from the factory.
Fluidic Self-Assembly: A manufacturing process, patented by Alien Technology.
It involves flowing tiny microchips in a special fluid over a base with holes shaped
to catch the chips.
Frequency: The number of repetitions of a complete
wave within one second. 1 Hz equals one complete waveform in one second. 1KHz equals
1,000 waves in a second. RFID tags use low, high, ultra-high and microwave frequencies.
Each frequency has advantages and disadvantages that make them more suitable for
some applications than for others.
GTAG (Global Tag): A standardization initiative of the Uniform Code Council
(UCC) and the European Article Numbering Association (EAN) for asset tracking and
logistics based on radio frequency identification (RFID). The GTAG initiative is
supported by Philips Semiconductors, Intermec, and Gemplus, three major RFID tag
High-frequency tags: They typically operate at 13.56 MHz. They can be read
from about 10 feet away and transmit data faster. But they are consume more power
than low-frequency tags.
A method of transmitting data
between tags and readers in which the antenna from the reader picks up changes in
the tag's antenna.
Industrial, Scientific, and Medical (ISM) bands:
A group of unlicensed frequencies
of the electromagnetic spectrum.
Integrated circuit (IC):
A microelectronic semiconductor device comprising
many interconnected transistors and other components. Most RFID tags have ICs.
See RFID reader
Low-frequency tags: They typically operate at 125 KHz. The main disadvantages
of low-frequency tags are they have to be read from within three feet and the rate
of data transfer is slow. But they are less expensive and less subject to interference
than high- frequency tags.
Memory: The amount of data that can be stored on a tag.
Microwave tags: Radio frequency tags that operate at 5.8 GHz. They have very
high transfer rates and can be read from as far as 30 feet away, but they use a
lot of power and are expensive.
Modulation: Changing the frequency or amplitude
of a wave to transmit data that is converted into digital form. For example, a wave
with the normal amplitude (or height) may be a one in binary code and a wave with
a lower amplitude might be a zero.
Multiple access schemes: Methods of increasing the amount of data that can
be transmitted wirelessly within the same frequency spectrum. RFID readers use Time
Division Multiple Access, or TDMA, meaning they read tags at different times to
avoid interfering with one another.
Multiplexer: An electronic device that allows a reader to have more than
one antenna. Each antenna scans the field in a preset order.
Nano-block: The term Alien Technology uses to describe its tiny microchips,
which are about the width of three human hairs.
Nominal range: The read range at which the tag can be read reliably.
Null spot: Area in the reader field that doesn't receive radio waves. This
is essentially the reader's blind spot. It is a phenomenon common to UHF systems.
Object Name Service (ONS): An Auto-ID Center-designed system for looking
up unique Electronic Product Codes and pointing computers to information about the
item associated with the code. ONS is similar to the Domain Name Service, which
points computers to sites on the Internet.
Passive tag: An RFID tag without a battery. When radio waves from the reader
reach the chip's antenna, it creates a magnetic field. The tag draws power from
the field and is able to send back information stored on the chip. Today, simple
passive tags cost around 50 cents to several dollars.
Patch antenna: A small square antenna made from a solid piece of metal or
Physical Markup Language (PML): An Auto-ID Center-designed method of describing
products in a way computers can understand. PML is based on the widely accepted
eXtensible Markup Language used to share data over the Internet in a format all
computers can use.
PML Server: A server that responds to requests for Physical Markup Language
(PML) files related to individual Electronic Product Codes. The PML files and servers
will be maintained by the manufacturer of the item.
Power level: The amount of RF energy radiated from a reader or an active
tag. The higher the power output, the longer the read range, but most governments
regulate power levels to avoid interference with other devices.
Programming: Writing data to an RFID tag.
Proximity sensor: A device that detects the presence of an object and signals
another device. Proximity sensors are often used on manufacturing lines to alert
robots or routing devices on a conveyor to the presence of an object.
Radio Frequency Identification (RFID):
A method of identifying
unique items using radio waves. Typically, a reader communicates with a tag, which
holds digital information in a microchip. But there are chipless forms of RFID tags
that use material to reflect back a portion of the radio waves beamed at them.
See read range
The process of turning radio waves from a tag into bits of information
that can be used by computer systems.
The maximum rate at which data can be read from a tag expressed
in bits or bytes per second.
Reader (also called an interrogator):
communicates with the RFID tag via radio waves and passes the information in digital
form to a computer system.
The area of coverage. Tags outside the reader field do not
receive radio waves and can't be read.
Tags that contain data that cannot be changed unless the
microchip is reprogrammed electronically.
The distance from which a reader can communicate
with a tag. Active tags have a longer read range than passive tags because they
use a battery to transmit signals to the reader. With passive tags, the read range
is influenced by frequency, reader output power, antenna design, and method of powering
up the tag. Low frequency tags use inductive coupling (see above), which requires
the tag to be within a few feet of the reader.
RFID tags that can store new information on its microchip.
San Francisco International Airport uses a read-write tag for security. When a bag
is scanned for explosives, the information on the tag is changed to indicate it
has been checked. The tag is scanned again before it is loaded on a plane. Read-write
tags are more expensive than read only tags, and therefore are of limited use for
supply chain tracking.
A microchip attached to an antenna that picks
up signals from and sends signals to a reader. The tag contains a unique serial
number, but may have other information, such as a customers' account number. Tags
come in many forms, such smart labels that are stuck on boxes; smart cards and key-chain
wands for paying for things; and a box that you stick on your windshield to enable
you to pay tolls without stopping. RFID tags can be active tags, passive tags and
An electronic device that can send and receive radio waves. When
combined with a digital signal processor that turns the waves into bits of information,
the scanner is called a reader or interrogator.
Similar to active tags, but the battery is used to run
the microchip's circuitry but not to communicate with the reader. Some semi-passive
tags sleep until they are woken up by a signal from the reader, which conserves
battery life. Semi-passive tags cost a dollar or more.
A device that responds to a physical stimulus and produces an electronic
signal. Sensors are increasingly being combined with RFID tags to detect the presence
of a stimulus at an identifiable location.
This term covers all business solutions enabled by tagging,
tracking, sensing and other technologies, including RFID, which make everyday objects
intelligent and interactive. When combined with continuous and pervasive Internet
connectivity, they form a new infrastructure that enables companies to collect data
and deliver services without human interaction.
A label that contains an RFID tag. It's considered "smart"
because it can store information, such as a unique serial number, and communicate
with a reader.
See contact less smart cards
See RFID Tag
Time Division Multiple Access (TDMA):
A method of solving
the problem of the signals of two readers colliding. Algorithms are used to make
sure the readers attempt to read tags at different times.
A radio transmitter-receiver that is activated when it receives
a predetermined signal. RFID tags are sometimes referred to as transponders.
Ultra-high frequency (UHF): Typically, tags that operate between 866 MHz
to 930 MHz. They can send information faster and farther than high- and low-frequency
tags. But radio waves don't pass through items with high water content, such as
fruit, at these frequencies. UHF tags are also more expensive than low-frequency
tags, and they use more power.
Uniform Code Council (UCC): The nonprofit organization that overseas the
Uniform Product Code, the barcode standard used in North America.
Uniform Product Code (UPC): The barcode standard used in North America.
It is administered by the Uniform Code Council.
Write rate: The rate at which information is transferred to a tag, written
into the tag's memory and verified as being correct.
See eXtensible Markup Language
XML Query Language (XQL):
A method of querying a database based on XML. Files
created using the Auto-ID Center's Physical Markup Language can be searched using