 A tag receiving the full power to operate from an integrated battery. Active tags transmits independently (ie they do not have to be excited by a reader) at regular intervals or in response to some form of stimulation (e.g. motion).
The range can easily exceed 50 metres, the drawback is they are quite bulky, expensive and have a limited lifespan (most commonly in order of few years).
The antenna (pl. antennae) is the primary physical device in both Reader and Tags to transmit/receive power and information using radio waves.
One of the way for a tag to communicate back to the reader, reflecting the incoming electromagnetic wave. The tags modulates the reflected signal modifying his radar cross section to encode information in the reflected signal. This is roughly equivalent to a communication using reflected light from a mirror, moving the mirror or interposing objects in front of the light beam to communicate using Morse code.
See also How Does RFID Work.
 The most common polarisation for RFID uses - the electromagnetic field oscillates constantly changing the orientation, allowing more freedom in positioning the tag.
 A dipole is probably the simplest form of antenna, composed of two "arms" stretching in opposite directions.It is the most common form of antenna found in UHF and MW tags.
The lenght of the dipole is related to the wavelength - with the half wavelenght folded dipole being the most common design.
The relative orientation of the dipole is essential for the correct operation of the RFID System. The dipole antenna has a linear polarisation, parallel to the antenna lenght.
The Effective Isotropic Radiated Power (EIRP) is a measure of the amount of Radio Frequency field emitted by the Reader using an ideal isotropic Antenna.
It is used primarily in the States - the FCC regulations dictate the maximum EIRP for an RFID reader.
The Electronic Product Code (EPC) in the SGTIN format (Serialized Global Trade Identification Number) is the standard pushed by EPCGlobal as a replacement for the EAN number in the future.
In its 96 bits implementation (Gen2), the unique ID is composed by a company prefix (20 to 40 bits), an item reference (24 to 4 bits) and a serial number (38 bits), while the older 64 bits implementation (used by Gen1) had fixed length company prefix (14 bits), item reference (20 bits) and serial number (25 bits),
EPCglobal is leading the development of industry-driven standards for the Electronic Product Code™ (EPC) to support the use of Radio Frequency Identification (RFID) in today’s fast-moving, information rich, trading networks.
They are a subscriber-driven organisation comprised of industry leaders and organisations focused on creating global standards for the EPCglobal Network™.
 The European Telecommunications Standards Institute (ETSI) is the organisation managing the allocation of frequencies and regulating the power levels allowed for RFID use in Europe
 The Federal Communications Commission is the governement agency managing the regulations for the frequencies and power levels allowed to be used for RFID in the US.
This is one of the most important parameter defining one particular RFID technology.
The frequencies used for RFID purposes are regulated by the law, and are falling in what is called the ISM band (the set of frequencies allowed for Industrial, Scientific and Medical applications), which is regulated at national level - so different countries force different frequencies for the same application. So, while the LF, HF and the MW (with minor changes) ranges are universally standardised, the UHF range is not.
However, being the frequencies used for UHF in different countries very close, it is possible to find wideband tags working properly in different countries.
EPCGlobal Gen1 is a relatively old UHF standard which has been superseded by EPCGlobal Gen2.
It featured readonly tags, with a thus factory programmed 64bits Unique ID.
The Inductive coupling (also called magnetic coupling) is the basic form of Near Field Communication.
See How Does RFID Work - Inductive Coupling.
 The International Organization for Standardization is an international-standard-setting body composed of representatives from various national standards organizations.
A large number of RFID technologies have a corresponding ISO standard.
As typical examples:
- ISO/IEC 14443 Identification, contactless and proximity cards
- ISO/IEC 18000 Part 3: Parameters for communications at 13.56 MHz
- ISO/IEC 18000 Part 6: Parameters for communications at 860 MHz to 960 MHz.
- Type C: EPCglobal Class 1 Gen 2.
Because of customers' privacy concerns, some RFID technologies (e.g. Gen2) implements a password protected kill command. A tag receiving the kill command disable itself in an irreversible way.
 Low frequency (LF) operates in the 125–148.5 kHz range.
It is probably the oldest and most deployed RFID technology, due to its simple operation. LF usually features a very short range, complete lack of anticollision and a very limited bandwidth, but it is very successful due to the fact it is mostly unaffected by metals and liquids, to the point it is used for animal tagging as an injected tag.
See also Technologies.
 Near Field Communication (NFC) is the main transmission mechanism between the readeder and the tag when their distance is considerably shorter than the wavelenght. The term gained a lot of press with the release of the Nokia NFC phones series.
See Inductive Coupling.
A tag receiving the full power to operate wirelessly from the reader's antenna.
This indicates the way the electromagnetic field is oscillating.
See Linear polarisation and Circular Polarisation.
 A portal is an antenna configuration meant to surround a doorway for people or vehicles, to track all the tags going through it.
Most commonly it is symmetrical, with antennae on both sides at different heights to increase the are covered. Some configurarions include antennae mounted on the ceiling and, less commonly, under the floor.
The reader is the main component in a RFID System, being the device able to read the tags.
Readers come in many shapes and prices and can be classified in "dumb" readers (they need a computer to operate, and they are often connected using a serial or usb connection) and intelligent readers (they include basic processing capabilities and can be remotely programmed, and they are more often connected to a nework).
While tags can are specifically designed to handle a single protocol, some reader are multi-protocol capable and are able to read different types of tags (usually with the limitation the protocols must work on the same frequency range).
We call a tag readonly when its content it is estabilished at production time and cannot be altered. Readonly tags usually just transmit an unique ID and tend to be much cheaper that writable tags.
A Real Time Locating System is a way of using RFID or similar technologies (e.g. WiFi) to determine the location of an item/person, usually by way of measuring the received signal levels (trilateration) or the directions the signal is coming from (triangulation) from fixed points.
A tag receiving part of the power it need to operate from an integrated battery. Usually, the integrated battery is only used to power the chip and not to enhance the transmission signal, still, semipassive tags obtain an increase in the reading range from four to tenfold compared to the passive tags.
Like active tags, they have a limited lifespan but, being the activation triggered by the presence of the reader, they tend to have a shorter life only when they are read frequently.
 A Smart Label is a normal printed label with an RFID tag embedded. The information in the label is usually encoded in three different ways:
- Human readable
- Barcode
- RFID Tag
This way, the information on the tag can be utilised in different and cost effective way, from the large depot reading the RFID tag, to the smaller regional warehouses using barcodes to the delivery staff reading the shipping address on the label.
 Surface Acoustic Wave (SAW) tags are tags using the properties of piezoelectric materials to encode an unique ID in the signal reflected by a tag.
This works converting the electromagnetic pulse picked up by the antenna into an acoustic wave, propagating along the surface of the tag. Appropriately spaced obstacles (encoding the unique ID) reflect back the wave to the antenna, where it is re-converted into a train of pulses which is picked back from the reader.
Being chip-less, they are readonly and they do not offer anticollision, but can withstand extremely harsh conditions (such the ones experienced in the Space Shuttle).
An alternative name for an RFID tag, combination of transmitter and receiver.
The main piece of information a tag is transmitting is its unique ID (or serial number). This is in the form of a long (many digits) number, having a length is usually expressed in bits.
As rough comparison, every 10 bits represents three digits when the number is expressed in decimal format. A 266 bits long ID would have a range of values comparable with the numbers of atoms in the universe (1080).
While the number is called "unique ID", for writable technologies it is not guaranteed to be unique - nothing prevent producing two tags with the same ID. For read only technologies, the fact the number is unique is dependent on the lenght of the ID, but for most applications even relatively short IDs can be considered "locally" unique.
When the serial number is writable, it is good practice (also standardised by GS1 for the Gen2 tags) to adopt a structured format.
 While RFID in the LF, HF and Microwave frequency ranges are standardised worldwide, UHF regulation change depending to the country.
However, while this usually requires different readers for every geographical area (or a multifrequency reader), the tags can be designed (with a minor performance penalty) to operate in a wider range of frequencies (wideband tags) , as they basically just "mirror back" the signal sent by the reader.
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Automatic Identification and Data Capture is the group of technologies whose purpose is to facilitate the transfer of data from physical objects to the ICT infrastructure.
In addition to RFID, other notable examples are barcodes, smart cards, magnetic stripes, optical character recognition (OCR) and biometric.
Anticollision is the protocol implemented at tag level to prevent the tags signals interfering with each other, while allowing reading multiple tags at the same time.
The additional memory in an RFID tag is often divided in logical sections called banks. Different banks can have different purposes (e.g. the Gen2 technology), or have different read of write passwords (e.g. MIFARE)
 The chip in an RFID tag is a silicon based processor which:
- containing the data, booth the unique ID and the additional memory
- has the communication protocols
- provides the Radio Frequency interface to the antenna
With few notable exceptions (SAW technology and semiconductive inks based tags) the large majority of RFID tags are based on silicon technology.
 While not technically an antenna, the coil is the way inductively coupled tags communicate with the reader.
It is composed from loops of conductive material, ranging from half a dozen loops made with etched metal or conductive ink in HF tags to many hundred copper wire loops for LF tags.
The main characterisic of a coil is the size of area surrounded. With a bigger the area, the tag is able to draw more power from the reader increasing its range. For LF tags, a ferromagnetic material is often used as core, whith the purpose of reducing the number of loops required.
The dwell time is the amount of time a tag stays in the reader's antenna field. The longer the dwell time, the higher the chances the tag will be successfully read. It is an important parameter for portals and antennas mounted to serve a conveyor belt.
The Effective Radiated Power (ERP) is a measure of the RF output emitted by the reader's antenna, ie the product of the power present at the antenna connector multiplied the antenna gain.
It is used primarily in Europe - ETSI regulations dictate the maximum ERP for an RFID reader.
 Electronic Article Surveillance (EAS) is a way to detect customers leaving a shop without paying for the goods they took.
While RFID offers a solution, it is too expensive to be used just for this purpose, and much cheaper chipless "1-bit tags" are used.
 The European Article Number (EAN) is an unique identification printed in common retail product boxes barcode. It is composed by 3 parts, identifying the Country, the Manufacturer and the Product.
It is managed by GS1, which also manages a similar code for the EPC Gen2 tags.
The Far Field is the electromagnetic field at a distance greater than the signal Wavelength - where proper electromagnetic field propagation takes place.
The most common form of communication using the far field is the Backscatter.
An RFID Reader meant to be installed in a fixed location, main powered and connected to external antennae, often to serve a portal.
With the exception of the ideal isotropic antenna, which spreads the power homogeneously in all direction, real antenna have an asymmetric radiation pattern, as they "squeeze" the field along a preferred area. So, dipole antennae radiation pattern is doughnut shaped, and patch antenna transmits more strongly in one direction.
The gain of the antenna is an indication of this factor as, while the total power emitted is constant, the strength of the field is greater in some parts - the gain is the ratio between the strength of the field in the preferred direction and the field of an idea isotropic antenna, measured in dB.
Designed to be the future replacement of barcodes, EPCGlobal Gen2 is an UHF technology featuring an extensible unique ID (96 bits in the earliest implementations), writable tags, support for up to 64Kbit in-tag memory and a password protected "kill" command to permanently disable the tag.
Thanks to a very good adaptive anticollision algorithm, it support theroretical rate of up to 600 tags detected per second.
The standard is designed to be extensible, and manufacturers have implemented both tags with onboard sensors (e.g. the CAEN temperature logger tag) or with an onboard battery (e.g. PowerID Semipassive tag) to increase the range.
It is the technology of choice of Wal Mart and the US Department of Defence.
The numbering scheme is managed by EPCGlobal, which is handling anything from container level tracking to item level tracking for the global supply chains.
 High Frequency (HF) RFID uses the spectrum around the worldwide standard frequency of 13.56MHz.
While LF is probably one of the most deployed technologies (being the oldest), HF technology is the one experiencing the biggest growt in the recent years.
See Technologies.
An assembled RFID tag, composed of the chip attached to the antenna and mounted on a substrate.
An RFID tag is called label when it is assembled on a paper or plastic backing with glue on one side, to facilitate the application on items such as cardboard boxes.
 Linear polarisation refers to the way the electromagnetic field oscillates in the space. A tag dipole antenna must be parallel to the polarisation to maximise the tag received power and signal.
A linearly polarised antenna is vertically or horizontally polarised.
The microwave range includes the spectrum between 1GHz and 300GHz (even if the division is quite arbitrary).
This is the range of frequencies also used by WiFi and Bluetooth, some RTLS and of course microwave ovens.
See also Technologies.
 A patch antenna is is the most common type of antenna used in UHF and Microwave RFID systems.
It is directional, covering only the front side with an aperture dependent on the antenna gain.
Patch antennae can be linearly or circularly polarised.
A battery operated reader, usually integrated with a portable computer, often a PDA.
An oscillating electromagnetic field (wave) with a frequency smaller than 300GHz.
Above that threshold, we have the Infrared range and the visible light - electromagnetic waves as well.
The range is the distance between the reader's antenna and the tag which allow the reader to consistently read the tag ID.
This has to be considered an indicative value - under certain conditions the range can be reduced or less frequently increased.
 The physical space covered by a reader's antenna, where a tag can be succesfully read. It is more indicative than the read range because real antennae are not covering the space in an uniform way.
 Smart Cards are electronic circuits packaged in a format complying to ISO/IEC 7810 (the "credit card" format). They have a limited amount of memory (few kilobytes), encryption (including some very strong forms) and they can communicate with the outside word using metallic contacts (contact smartcards) and RFID - most often HF (contactless cards).
The layer providing physical backing for an RFID tag.
The tag is the physical information carrying device in an RFID system.
A tag is a small and cheap radio transmitter, which uses radio waves to transmit some information (an unique id, sometime additional data) back to the reader.
A tag is composed or three elements: a substrate, and antenna and a chip.
An alternative name for an RFID tag, combination of transmitter and responder.
Ultra High Frequency includes the range of electromagnetic frequencies from 100MHz to 1GHz.
Post of the communication systems operating today (including TV, radio and mobile phones) uses this range of frequency. Only a small part of the UHF range is allocated to RFID, and which part is differs country by country.
See also Technologies.
 The wavelength of an electromagnetic waves is the spatial distance between two successive peaks of the signal. It influences the length of the antenna in UHF and MW frequency ranges, and also determines the transition point between Near Field and Far Field.
The Write Range is the effective distance a tag can be successfully written. It is usually reduced compared to the read range, because of the additional power needed during the writing phase.
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