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Glossary Of Terms

This document sets out to review all the RFID terms, standards, and references within the RFID market that exists today. The list is not all encompassing, but it does give accurate definitions of industry terminology that is useful to both RFID novices and experts.

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Active tag: An RF tag (transponder) that uses batteries as a partial or complete source of power. Batteries may be replaceable or sealed in. Active tags are more expensive and have much longer read ranges than passive tags. They are typically used to track expensive items over long ranges.

Addressability: The ability to address bits, fields, files, or other portions of memory in a tag.

AFI (Application Family Identifier): Represents the type of application being targeted by the reader. It is used to ensure that information is only extracted from those transponders (tags) meeting the required application criteria. In other words, it is used to filter out information from other present transponders that are not relevant to the application.

AIM (Association for Automatic Identification and Mobility): The global trade association for the Automatic Identification and Data Capture (AIDC) industry.

Alignment: The orientation of the tag (transponder) relative to the reader antenna in pitch, roll and yaw. This is sometimes referred to as the coupling.

Amplitude: The height of a wave

AM (Amplitude Modulation): Data is contained in changes in the amplitude of the signal.

Antenna: The conductive elements that radiate and receive the RF energy between tags and readers. Every tag (transponder) consists of an IC chip connected to an antenna. Readers are typically outfitted with multiple antennas,which are positioned for optimal alignment (or coupling) with the transponders.

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.

ASCII: American Standard Code For Information Exchange. A computer code consisting of 128 alphanumeric and control characters, each encoded with 7 bits, used for the exchange of information between computer devices

ASCII protocol: The protocol used to send ASCII character commands to the reader.

Asynchronous Transmission: A method of transmission that doesn't require timing information in addition to data. The beginnings and ends of characters, or blocks of characters, are indicated by start and stop bits.

Automatic Identification and Data Capture (AIDC): The various methods of collecting data and entering it directly into computer systems without human involvement. Technologies normally considered part of AIDC include bar code scanning, biometrics, RFID, and voice recognition.

ATI: Antenna Tuning Indicator

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.

Capacity: The number of bits or bytes that can programmed into a tag. This may represent the bits accessible to the user or the total number including those reserved for the manufacturer (i.e. parity or control bits)

Capture Field: The region of the electromagnetic field, generated by the antenna, in which transponders will operate.

Carrier Frequency: The main frequency of a transmitter which is then modulated to transmit information (see also: 'Modulation')

CCITT: Comite Consultatif International Telegraphique Telephonique. An international body that produces standardization recommendations.

CE: The CE Mark. Is a symbol used by the European Community to indicate that the item has passed certain safety and emission standards.

CEPT: Conference of Posts and Telecommunications. The body responsible for European standardization and harmonization of radio communications.

Closed loop systems: RFID tracking systems that do not need to communicate with external trading partners. Since the tracked item never leaves the company's control, it does not need to inter-operate with other companies' RFID infrastructures. Therefore, the solution can use the protocol, frequency, and data format that work best for the application, without regard for open standards.

Closed loop applications include: electronic article surveillance (EAS), toll collection, mobile and returnable asset management, container tracking, livestock tracking, airport baggage handling, and homeland security. Many of these applications use low frequency (125 KHz) and high frequency (13.56 MHz) RFID transponders.

Code Plate: See 'Tag'

Controller: See "Multiplexer"

Corruption: When systems have poor error checking protocols, the possibility exists that data reported by the reader is not the data transmitted by the transponder. This is defined as corrupted data.

Coupling: (See also 'alignment') Electromagnetic Coupling describes systems that use a magnetic field as a means of transferring data or power. Electrostatic Coupling is used to describe systems that induce a voltage on a plate as a means of transferring data or power. Inductive coupling describes a method of transmitting data between tags and readers in which the antenna from the reader picks up changes in the tag's antenna.

CRC: Cyclic Redundancy Check

CRC-CCITT: An internationally defined method for mathematically generating a CRC

Data Transfer Rate: The number of characters that can be transferred within a given time

DC: Direct Current

De-tuning: The change in performance of transponders and readers caused by the presence of metal, or ferromagnetic materials

DIN: Deutsche Industrie-Norm. The standards body in Germany

DIP: Dual In-line Package

DRB: Digital Receiver Board

DSFID: Data Storage Format Identifier - Indicates how the data is structured in the transponder's memory

Duplex: Full Duplex (FDX) - A channel capable of transmitting data in both directions at the same time. Half Duplex (HDX) - A channel capable of transmitting data in both directions, but not at the same time.

EAN (European Article Numbering): The standard used for bar coding throughout Europe, Asia, and South America. EAN International is the administering organization.

EEPROM (Electrically Erasable Programmable Read-Only Memory): 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 being used without creating electromagnetic interference.

Electromagnetic interferance (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 potentially interfere with RFID tags.

Electronic article surveillance (EAS): RFID based technology used by retailers to deter theft. When an article is purchased (or borrowed from a library), the tag is removed or turned off. If an article passes through a read zone with a live tag, an alarm sounds.

Electronic Label: A label that has an electronic RFID tag embedded inside or on it. Also referred to as a smart label

Electronic Product Code (EPC): An item identification system based on RFID that includes technical specifications for the RFID system plus a structure and syntax for company identification codes, item naming conventions, and Web-based distributed data bases. Jointly administered by the Uniform Code Council and EAN International under the auspices of EPCglobal.

Encryption of Data: A method of scrambling data to prevent unauthorized use or duplication.

EOF: End Of Frame

EPC Network: EPCglobal (a consortium of UCCNET, EAN International, and the Auto-ID center) is a neutral, consensus-based, standards organization. Its mission is to develop and manage standards for the EPC Network, including specifications for: EPC tag data, air interface protocols for Class 0, Class 1, and UHF Generation 2, RFID Savant Server, RFID Physical Markup Language (PML), and RFID Object Naming Services (ONS).

Error correcting code: A code stored on an RFID tag to enable the reader to determine the value of missing or erroneous bits of data. For a 32 bit data transmission, 7 additional bits are required.

Error correcting mode: A mode of data transmission between the tag and reader in which missing or erroneous bits are automatically corrected.

Error correcting protocol: The rules by which the error correcting mode operates.

Error Rate: The number of errors per number of transactions.

ESD: Electro-static discharge. The build-up of electrical potential that can cause damage to electronic modules

ETSI: European Telecommunications Standards Institute. The body that recommends standards for adoption by European Community (EC) member countries.

Excite: The reader "excites" a passive tag when it transmits RF energy to wake up the tag and enable it to transmit back.

Exciter: The electronics which drive an antenna are called the exciter or transmitter. Together with the antenna they are called a scanner.

eXtensible markup language (XML): A widely accepted method of sharing information over the Internet between computers with different operating system.

Factory programmed: Read-only RFID tags have information (an identification number) written into the silicon microchip during the manufacturing process.

False Activation: When a 'foreign' transponder enters the field of an RF system and triggers an erroneous activation.

FCC: Federal Communications Commission. The US regulatory body for radio equipment.

Field Programming: Programming information onto the tag after it has been shipped from the manufacturer to an OEM customer, and end user, or one of the manufacuter's distribution centers. Field programming usually occurs before the tag is installed on the object to be identified. This approach enables the introduction of application specific data into the tag at any time.

Field Protection: The ability to limit the operations which can be performed on portions or fields of the data stored in a tag.

Field Strength: The strength of the electro-magnetic signal at a specified distance from the transmitting antenna. The legal field strength limits vary by country.

Firmware: Microprocessor programming instruction sets that are stored in a memory unit rather than being implemented through software. Most manufacturers of readers and RFID-enabled printers plan to use Firmware to upgrade their products to support future EPC specifications (i.e. the UHF Generation 2 air-interface protocol).

Flat Panel Antenna: Flat, conductive sheet antennas, usually made of metal plate or foil.

FM: Frequency Modulation - Data is contained in changes the frequency of the signal. In the binary form, the data is contained in the changes between two frequencies of the signal and is known as FSK.

FM/FSK: Frequency Modulation/Frequency Shift Keying

Fluidic Self-Assembly: A manufacturing process, patented by Alien Technology.

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. The spectrum can be divided into the following frequency bands:

VLF Very Low Frequency 3 KHz to 30 KHz
LF Low Frequency 30 Khz to 300 KHz - Typically 125 KHz Short read range (3 ft); slow data transfer; Less Expensive; less prone to interference
MF Medium Frequency 300 KHz to 3 MHz
HF High Frequency 3 MHz to 30 MHz - Typically 13.56 MHz Read range about 10 feet; faster data transfer; consume more power than LF
VHF Very High Frequency 30 MHz to 300 MHz
UHF Ultra High Frequency 300 MHz to 3 GHz

900 to 950 MHz is the range of EPC class 0, class 1, and UHFG2 tags. Anything above 1GHz is considered micro-wave
Longer Read Range (15 feet); faster data transfer; lower penetration through items with high water content;
Micro-Wave Micro-Wave Up to 5.8 GHz Read range up to 30 feet; very high data transfer rates; high power consumption; expensive.

FSM: Field Strength Meter

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.

Hands Free: A situation where no deliberate presentation of the transponder is required to initiate an identification.

Harmonics: In addition to the radio output at its principal frequency, a transmitter produces lesser bursts of power at multiples of that frequencty. These diminishing outputs are called harmonics (see also: 'Spurious Emissions')

Hz: Hertz

High-frequency tags: See 'Frequency'

IC: Integrated Circuit

ID: Identification

Inductive coupling: A system that uses the inducing of a current in a coil as a means of transferring data or power. This is sometimes used as a method of transmitting data between tags and readers.

In Use Programming: The ability to read from and write data to the tag while it is attached to its object. Tags and systems with this capability are called read/write tags and systems.

Interference: Unwanted electrical signals found in the operating environment of RFID equipment that interfere with the normal operation of transponders and readers.

Interrogator: See Reader and Programmer

ISM Band: A portion of the radio spectrum designated for Industrial, Scientific, and Medical use.

License Plate: A concept where the fixed code contained in an RF transponder is used as a pointer to a database, in the same way that your name and address information can be determined through the license plate on your car (See also: 'Read Only').

Life: Functional period within which no maintenance, adjustment, or repair is to be reasonably expected.

Low-Frequency Tags: See 'Frequency'

mA: Milliampere

Master: In many communications protocols, problems with collision or corruption of data might occur if all devices communicate at the same time. One way to overcome this problem is to define one device as the master and all other connected devices as slaves. Only the master can initiate communications, and no slave is allowed to communicate unless instructed to do so.

Memory: The amount of data that can be stored on a tag.

Memory Card: A read/write or reprogrammable tag the size of a credit card

Memory Module: A read/write or reprogrammable tag

Microwave tags: See 'Frequency'

Modulation: The methods of altering the signal between reader and transponder (tag) in order to carry the encoded information. In some cases, different modulating techniques are used in each direction (to and from the tags). The various methods include:

  • Amplitude Modulation (AM): Data is contained in changes in amplitude of the carrier
  • Frequency Modulation (FM): Data is contained in the changes in the frequency of the carrier.
  • Frequency Shift Keyed Modulation (FSK): Data is contained in the changes between two frequencies of carrier
  • Phase Modulation (PM): Data is contained in the changes in the phase of the carrier.
  • Pulse Duration Modulation (PDM): Data is contained in the duration of the pulses. Also known as Pulse Width Modulation (PWM)
  • Pulse Position Modulation (PPM): Data is contained in the position of pulses relative to a reference point
  • Continuous Wave Modulation (CW): Data is contained in a carrier that is switched on and off
MPR (Multi-Protocol Reader): A reader capable of handling two or more communication protocols

MPT: Multi-page Transponder

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: A switching device that supports multiple readers or antennas by checking each in accordance with a prescribed scheduling scheme and priority. Also referred to as multichannel readers or controllers.

MUX: Multiplexer

NanoBlock: The term Alien Technology uses to describe its tiny microchips, which are about the width of three human hairs.

Noise: Unwanted ambient electrical signals found in the operating environment of RFID equipment (See also: 'Interference')

Noise Immunity: An indication of the robustness of a system to operate in the presence of electrical interference

Nominal range: The read range at which the tag can be read reliably, considering the normal variability of the environment in which it is used.

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): System for looking up unique Electronic Product Codes and pointing computers to information about the item associated with the code. ONS is to RFID as the Domain Name Service, is to TCPIP on the Internet.

Omnidirectional: Capability of a tag to operate in any orientation

Open loop RFID: open loop RFID applications such as supply chain solutions envisioned by large retailers, require interoperability between trading partners. apability of a tag to operate in any orientation

Orientation: Alignment of a tag with respect to the reader antenna

Parity: A technique used to detect data transmission errors by adding an extra bit to each character.

Passive tag: An RFID tag without a battery. It is usually powered by the electromagnetic field generated by the reader antenna.

Penetration: Term used to indicate the ability of a particular radio frequency to pass through non-metallic materials. Low frequency tagging systems are said to have good penetrative properties as their transponders can be read when behind or encased in other materials. Microwave tagging systems, while having greater read ranges, have poor penetrating properties.

Physical Markup Language (PML): Method of describing products in a way computers can understand. PML is based on eXtensible Markup Language used to share data over the Internet in a format all computers can use.

Pick Rate: The percentage detection rate for an RF system. This is a function of the speed of throughput, transponder orientation, number of transponders present, etc.

PLC: Programmable Logic Controller

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 level of power that radiate from a reader or tag, usually measured in volts/meter. The higher the power output, the longer the read range. 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.

Range: The maximum distance between the antenna and a transponder at which the signals can be properly received, either for reading the data encoded in the transponder, or for reprogramming it. Typically the write range is about 70% of the read range.

Read: The process of obtaining the information encoded in the tag.

Read rate: The maximum rate at which data can be read from a tag expressed in bits or bytes per second.

Reader (Interrogator): The device containing the digital electronics to interpret the modulated tag data, separate the data from the formatting and error management bits, and transmit the data in digital form to a host computer or programmable logic controller.

Reader field: The area of coverage. Tags outside the reader field do not receive radio waves and can't be read.

Read-only tags: A tag that has information written to it during its manufacture. This information can only be read from the tag, never changed.

Read-write tags: Tags that are capable of being re-programmed to change existing data or add new data, while the tag is attached to the object it identifies. This capability is referred to as in-use programming, and tags with this capability are referred to as re-programmable, read/write tags, memory cards, and memory modules.

Reader/Writer: An electronic device that can act as both a reader and programmer for an RF transponder, typically while the transponder is attached to the object it identifies

RFID tag: A microchip attached to an antenna that picks up signals from and sends signals to a reader. The tag contains a unique serial number, and may also have other information encoded to it.

Scanner: 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.

Semi-passive tag: Similar to active tags, but the battery is only used to run the microchip's circuitry, 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.

Sensor: A device that responds to a physical stimulus and produces an electronic signal. Sensors are increasingly being combined with RFID tags in industrial automation applications.

Smart label: A label that contains an RFID tag.

Smart card: A credit card or loyalty card that contains an RFID chip to transmit information without having to be swiped through a reader

Tag: The data carrier in an RFID system that communicates with the reader. Also referred to as 'Transponder'

TAV (Total Asset Visibility): A supply chain initiative by the U.S. Department of Defense to identify all assets from initial shipment through eventual disposal. Much of the TAV program is based on the sue of both active and passive RFID technology.

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.

Transmitter (Exciter): The electronics that drive an antenna are called the transmitter or exciter. Together with the antenna and a receiver they are called a reader or scanner

Transponder: An electronic TRANSmitter /resPONDER which is attached to the object to be identified and, when appropriate signals are received, transmits information as radio signals to a trader. Also referred to as 'Tag'

Ultra-high frequency (UHF): See 'Frequency'

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.

Verify: To assure that the intended operation was correctly performed.

WORM (Write Once Read Many): Tags that, once written to, cannot rewritten or changed. Also called 'Read Only'

Write rate: The rate at which information is transferred to a tag, written into the tag's memory and verified as being correct. Measured in bits or bytes per second.