Markets & Technologies > Identification > Glossary > Basics of RFID. What is RFID? How it works? What are target Applications?

IDENTIFICATION

Advantage of RFID System

The full advantages of RFID can be realised when the application, manufacturing process and the supply chain are considered as a whole. One of the unique differentiators for RFID in comparison to other identification technologies, is the ability to send and receive data, in a so-called downstream and upstream process. Products can therefore be identified from the raw materials stage to complete manufacture, quality assurance, registration in the warehouse and delivery to the customer right through to servicing. This truly unlocks the full potential of RFID.

Air interface

The conductor free medium, usually air, between a transponder and a reader/interrogator through which data communication is achieved by means of a modulated inductive or propagated electromagnetic field.

Alphanumeric

Strictly data comprising both alphabetical and numeric characters. For example, A1234C9 as an alphanumeric string. The term is often used to include other printable characters such as punctuation marks.

Amplitude

The maximum absolute value of a periodic curve measured along its vertical axis (the height of a wave, in layman's terms).

Amplitude modulation

Changing the amplitude of a radio wave. A higher wave is interpreted as a 1 and a normal wave is interpreted as a zero. By changing the wave, the RFID tag can communicate a string of binary digits to the reader. Computers can interpret these digits as digital information. The method of changing the amplitude is known as amplitude shift keying, or ASK.

Amplitude shift keying

Changing the amplitude of the wave to communicate data stored on a tag.

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.

API

API: A source-code interface provided by a computer system or program library to support a computer program's requests for services. Unlike an application binary interface, an API is specified in terms of a programming language that can be compiled when an application is built, rather than an explicit low-level description of how data is laid out in memory.

Applet

A software component designed to run in the context of another program, such as a Web browser.

Application Programming Interface

A source-code interface provided by a computer system or program library to support a computer program's requests for services. Unlike an application binary interface, an API is specified in terms of a programming language that can be compiled when an application is built, rather than an explicit low-level description of how data is laid out in memory.

Application-Specific Integrated Circuit (ASIC)

An integrated circuit (IC) customized for a particular use (such as a chip designed solely to run a cell phone) rather than general use.

Asset Tracking

One of the most common applications for RFID. Placing RFID transponders on or in high-value assets and returnable transport containers enables companies to gather data on their location quickly and with little or no manual intervention. Tagging assets allows companies to increase asset utilization, identify the last known user of assets, automate maintenance routines and reduce lost items.

Attenuation

The reduction of energy.

Attenuator

A device that attaches to a transmission line (a coaxial cable) that reduces the power of the RF signal as the signal travels through the cable from the reader to the antenna. Attenuators usually work by dissipating the RF energy as heat.

Bandwidth

The range or band of frequencies, defined within the electromagnetic spectrum, that a system is capable of receiving or delivering.

Block check character (BCC)

A parity error checking character added to data for the purposes of detecting transmission errors.

Capacity – Channel

A measure of the transmission capability of a communication channel expressed in bits.s-1 and related to channel bandwidth and signal to noise ratio by the Shannon equation;

Capacity – Data

A measure of the data, expressed in bits or bytes, that can be stored in a transponder. The measure may relate simply to the bits that are accessible to the user or to the total assembly of bits, including data identifier and error control bits.

Carrier

Abbreviated term for Carrier Frequency.

Carrier Frequency

The frequency used to carry data by appropriate modulation of the carrier waveform, typically in a radio frequency identification system, by amplitude shift keying (ASK), frequency shift keying (FSK), phase shift keying (PSK) or associated variants.

Channel

A medium or medium associated allocation, such as carrier frequency, for electronic communication.

Channel decoding

The process of operating upon a received transmission to separate the source-encoded data from the channel encoded form.

Channel encoding

The application of coding schemes to facilitate effective channel transmission of the source encoded data.

Character set

A set of characters assembled to satisfy a general or application requirement.

Clocking information

Timing signals or pulses used to synchronize the transfer of data from a source to a host destination.

Concatenation

The facility to link together specific items of data, held in data carriers, to form a single file or field of data.

Continuous Wave Modulation (CW)

A data modulation scheme in which the data is represented by the carrier signal being switched on and off. The scheme is identical to amplitude shift keying (ASK) with 100% depth of modulation – known as on-off keying (OOK).

Corruption-data

In data terms, the manifestations of errors within a transmitted data stream due to noise, interference or distortion.

CRC - Cyclic Redundancy Check

An error detection algorithm which exploits the attributes of modulo-2 arithmetic to generate, through the use of a generator polynomial, a transmission polynomial, comprising the message polynomial and a parity polynomial.

Cryptographic coprocessor

Special circuitry that perform cryptographic calculations, such as modular arithmetic and large integer calculations. These circuits are added to a standard processor core and therefore are called coprocessors.

Data

Representations, in the form of numbers and characters for example, to which meaning may be ascribed.

Data Field

A defined area of memory assigned to a particular item or items of data.

Data Field Protection

The facility to control access to and operations upon items or fields of data stored within the transponder.

Data Identifier

A specific character, or string of characters, that denotes the nature or intended use of the data that follows.

Data transfer

The process of transferring data from a data holding source to a destination.

Demodulation

Process of recovering channel encoded data from a modulated carrier waveform.

Die

The silicon block onto which circuits have been etched to create a microchip.

Dielectric

Unable to conduct direct electric current. Dielectric substances are used as insulators.

Dielectric constant

The measure of a material’s ability to store a charge when an electric field is applied, or its "capacitance.” If a material has a high dielectric constant, it reflects more RF energy and detunes the antenna more, which makes it harder to tag. Examples of materials with a low dielectric constant are dry paper (2), plastics (most are between 2 and 4), and glass (between 5 and 10). Water’s dielectric constant changes: At room temperature it is 80; near boiling it is 55; and when frozen it is 3.2.

Dipole (antenna)

A fundamental form of antenna, comprising a single conductor of length approximately equal to half the wavelength of the carrier wave. Provides the basis for a range of other more complex forms of antenna.

Direct Sequence Spread Spectrum (DSSS)

A category of spread spectrum modulation in which the source base-band bit stream is multiplied by a fast pseudorandom binary sequence to produce a signal that exhibits broad-band characteristics. Alternatively, the pseudorandom sequence and its inverse are used to represent logic 1 and 0.

Directivity–antenna

The ability of an antenna to concentrate radiated energy in a preferred direction, when considered in a transmitter mode. Alternatively, the ability to reject signals that are off-axis to the normal of the antenna, when considered in the receiver mode. May be expressed as a ratio of power radiated per unit solid angle in a defined direction to the total power radiated by the antenna.

Dispersion – pulse

The spread in duration and form experienced by a pulse in transmission through a communication channel.

Distortion

Any disturbance that causes an unwarranted change in the form or intelligibility of a signal. The distortion exhibits a noise-like effect that can be quantified as the ratio of the magnitude of the distortion component to the magnitude of the undistorted signal, usually expressed as a percentage.

Effective Aperture

A term denoting the reception capability of a practical antenna expressed as the product of actual aperture and antenna efficiency.

Effective Isotropic Radiated Power (EIRP)

The product of the input power to an antenna and the gain relative to an isotropic source.

Electromagnetic interference

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.

Electromagnetic spectrum

The range or continuum of electromagnetic radiation, characterised in terms of frequency or wavelength.

Electromagnetic wave

A sinusoidal wave in which electric E and magnetic H components or vectors can be distinguished at right angles to one another, and propagating in a direction that is at right angles to both the E and H vectors. The energy contained within the wave also propagates in the direction at right angles to the E and H vectors. The power delivered in the wave is the vector product of E and H (Poynting Vector).

Electronic Data Interchange (EDI)

Communication of a data message, or messages, automatically between computers or information management systems, usually for the purposes of business transactions.

Electronic Data Transfer (EDT)

The transfer of data by electronic communication means from one data handling system to another.

Error

In digital data terms, a result of capture, storage, processing or communication of data in which a bit or bits assume the wrong values, or bits are missing from a data stream.

Error burst

A group of bits in which two successive erroneous bits are always separated by less than a given number of correct bits.

Error control

Collective term to accommodate error detection and correction schemes applied to handle errors arising within a data capture or handling system.

Error correcting code (ECC)

Supplemental bits introduced or source encoded into a data stream to allow automatic correction of erroneous bits and/or derivation of missing bits, in accordance with a specific computational algorithm.

Error correcting mode

Mode defined for a data communication or handling process in which missing or erroneous bits are automatically corrected.

Error correcting protocol

The rules by which an error correcting mode operates.

Error correction

A term to denote a scheme or action for correcting an error detected in a data stream.

Error detection

A term to denote a scheme or action to determine the presence of errors in a data stream.

Error management

Techniques used to identify and/or correct errors within a data capture and handling system with the objective of assuring the accuracy of data presented to the system user.

Extended Binary Coded Data Interchange Code (EBCDIC)

An eight-bit binary code set, sometimes referred to as extended ASCII, wherein the 128 character set of ASCII are accommodated, together with other characters and control functions, making up a total set of 256 characters.

Far Field

The region of an electromagnetic radiation field at a distance from the antenna in which the field distribution is unaffected by the antenna structure and the wave propagates as a plane wave.

Form factor

The packaging in which a transponder can be put. These include thermal transfer labels, plastic cards, key fobs and so on.

Frequency

The number of cycles a periodic signal executes in unit time. Usually expressed in Hertz (cycles per second) or appropriate weighted units such as kilohertz (kHz), Megahertz (MHz) and Gigahertz (GHz).

Frequency Hop Rate

The frequency at which a frequency hopping spread spectrum (FHSS) system moves between transmission frequencies. It is equal to the reciprocal of the dwell time at a FHSS centre frequency.

Frequency Hop Sequence

A pseudorandom binary sequence (PRBS) determining the hopping frequencies used in frequency hopping spread spectrum (FHSS) systems.

Frequency Hopping Spread Spectrum (FHSS)

A category of spread spectrum modulation in which each bit of data is divided into chips and each chip is represented by a different spectral component or tone in the spread spectrum band using a pseudorandom sequence to assign tones. Modulated in this way the transmissions hop from frequency to frequency within the band, requiring a receiver synchronized to the pseudorandom chipping sequence to recover the data.

Frequency Modulation (FM)

Representation of data or signal states by using different transmission frequencies. Where data is in binary form, the modulation constitutes two transmission frequencies and is referred to as Frequency Shift Keying (FSK).

Frequency Shift Keying (FSK)

Representation of binary data by switching between two different transmission frequencies.

Half Duplex (HDX)

A channel communications protocol that allows a channel to transmit data in both directions but not at the same time. In RFID, the method of information exchange in which the information is communicated after the transceiver has stopped transmitting the activation field.

Handshaking

A protocol or sequence of signals for controlling the flow of data between devices, which can be hardware implemented or software implemented.

Harmonics

Multiples of a principal frequency, invariably exhibiting lower amplitudes. Harmonics can be generated as a result of circuit non-linearities associated with radio transmissions resulting in harmonic distortion.

Hexadecimal (Hex)

A column placing method of representing data to the base of 16, using digits 0-9 and letters A to F for decimal values 10 - 15. For example, 1010 = A16 and 2210 = 6F16 Used as a convenient short hand notation for representing 16 and 32 bit memory addresses.

Host system

A computer on a network, which provides services to users or other computers on that network.

Hysteresis

A retardation of an effect when the forces acting upon a body are changed. When corrugated boxes and other materials absorb water and then dry, they are never as RF-friendly as they were before they became moist.

ID Filter

A software facility that compares a newly read identification (ID) with those within a database or set, with a view to establishing a match.

Impact

Any influence upon a system, environmental or otherwise, that can influence its operational performance.

Incorrect Read

The failure to read correctly all or part of the data set intended to be retrieved from a transponder during read or interrogation process. Alternative term for Misread.

Interchangeability

The condition that exists between devices or systems that exhibit equivalent functionality, interface features and performance to allow one to be exchanged for another, without alteration, and achieve the same operational service. An alternative term for compatibility.

Interface

A physical or electrical interconnection between communicating devices.

Interference

Unwanted electromagnetic signals, where encountered within the environment of a radio frequency identification system, cause disturbance in its normal operation, possibly resulting in bit errors, and degrading system performance.

Interoperability

The ability of systems, from different vendors, to execute bi-directional data exchange functions, in a manner that allows them to operate effectively together.

Intersymbol Interference

Interference arising within a serial bit stream as a result of pulse dispersion and consequential overlapping pulse edges, leading possibly to decoding errors at the receiver.

Isotropic source

An ideal electromagnetic source or radiator exhibiting a perfect spherical energy radiation pattern.

Manchester coding

A bi-phase code format in which each bit in the source encoded form is represented by two bits in the derived or channel encoded form. The transformation rule ascribes 01 to represent 0 and 10 to represent 1.

Memory Modules

Colloquial term for a read/write or re-programmable transponder.

Microwave

A high-frequency electromagnetic wave, one millimeter to one meter in wavelength.

Modulation

A term to denote the process of superimposing (modulating) channel encoded data or signals onto a radio frequency carrier to enable the data to be effectively coupled or propagated across an air interface. Also used as an associative term for methods used to modulate carrier waves. Methods generally rely on the variation of key parameter values of amplitude, frequency or phase. Digital modulation methods principally feature amplitude shift keying (ASK), frequency shift keying (FSK), phase shift keying (PSK) or variants.

Modulation Index

The size of variation of the modulation parameter (amplitude, frequency or phase) exhibited in the modulation waveform.

Multiplexor (Multiplexer)

A device for connecting a number of data communication channels and combining the separate channel signals into one composite stream for onward transmission through a single link to a central data processor or information management system. At its destination the multiplexed stream is de-multiplexed to separate the constituent signals. Multiplexors are similar to concentrators in many respects, a distinction being that concentrators usually have a buffering capability to ‘queue’ inputs that would otherwise exceed transmission capacity.

Noise

Unwanted extraneous electromagnetic signals encountered within the environment, usually exhibiting random or wide band characteristics, and viewed as a possible source of errors through influence upon system performance.

Noise immunity

A measure of the extent or capability of a system to operate effectively in the presence of noise.

Parity

A simple error detecting technique, used to detect data transmission errors, in which an extra bit (0 or 1) is added to each binary represented character to achieve an even number of 1 bits (even parity) or an odd number of 1 bits (odd parity). By checking the parity of the characters received a single errors can be detected. The same principle can be applied to blocks of binary data.

Penetration

Term used to indicate the ability of electromagnetic waves to propagate into or through materials. Non-conducting materials are essentially transparent to electromagnetic waves, but absorption mechanisms, particularly at higher frequencies, reduce the amount of energy propagating through the material. Metals constitute good reflectors for freely propagating electromagnetic waves, with very little of an incident wave being able to propagate into the metal surface.

Phase Modulation (PM)

Representation of data or signal states by the phase of a fixed frequency sinusoidal carrier wave. Where data is in binary form the modulation involves a phase difference of 180o between the binary states and is referred to as Phase Shift Keying (PSK).

Phase Shift Keying (PSK)

Representation of binary data states, 0 and 1, by the phase of a fixed frequency sinusoidal carrier wave, a difference of 180o being used to represent the respective values.

Polar Field Diagram

A graphical representation of the electric or magnetic field intensity components of an electromagnetic field, expressed on a polar co-ordinate system (distance v angle, through 360o). Typically used to illustrate the field characteristics of an antenna.

Polarisation

The locus or path described by the electric field vector of an electromagnetic wave, with respect to time.

Power-levels and flux density

The vector product of electric and magnetic field strengths within an electromagnetic wave, expressed as levels in watts and as a power flux density, measured at a distance from the source, in watts per square meter (W.m-2). Low power radio frequency transmissions are generally expressed in milli- or microwatts.

Protocol

A set of rules governing a particular function, such as the flow of data/information in a communication system.

Proximity

Term often used to indicate closeness of one system component with respect to another, such as that of a transponder with respect to a reader.

Proximity sensor

An electronic device that detects and signals the presence of a selected object. When used in association with a radio frequency identification system the sensor is set up to sense the presence of a tagged or transponder carrying object when it enters the vicinity of the reader/interrogator so that the reader can then be activated to effect a read.

Pulse dispersion

The spread in width or duration of a pulse during transmission through a practical transmission system, due to the influence of distributed reactive components

Read

The process of retrieving data from a transponder and, as appropriate, the contention and error control management, and channel and source decoding required to recover and communicate the data entered at source.

Read Only

Term applied to a transponder in which the data is stored in an unchangeable manner and can therefore only be read.

Read/Write

Applied to a radio frequency identification system, it is the ability to both read data from a transponder and to change data (write process) using a suitable programming device.

Readability

The ability to retrieve data under specified conditions.

Redundancy

In information terms it is a term to describe the additional bits, such as those for error control or repeated data, over and above those required for transmitting the information message.

Reprogrammability

The ability to change the data content of a transponder using a suitable programming device.

RS232

A common physical interface standard specified by the EIA for the interconnection of devices. The standard allows for a single device to be connected (point-to-point) at baud values up to 9600 bps, at distances up to 15 meters. More recent implementations of the standard may allow higher baud values and greater distances.

RS422

A balanced interface standard similar to RS232, but using differential voltages across twisted pair cables. Exhibits greater noise immunity than RS232 and can be used to connect single or multiple devices to a master unit, at distances up to 3000 meters.

RS485

An enhanced version of RS422, which permits multiple devices (typically 32) to be attached to a two wire BUS at distances of over one kilometer.

Scrambling

The rearrangement or transposition of data to enhance security of stored data or the effectiveness of error control schemes.

Screening

The process of avoiding or minimizing electromagnetic interference by use of electromagnetic reflective and absorptive materials suitably structured or positioned to reduce interaction between the source of potential interference and the circuit being protected.

Sensor

An electronic device that senses a physical entity and delivers an electronic signal that can be used for control purposes.

Separation

A term used to denote the operational distance between two transponders.

Signal to Noise & Distortion (SINAD)

The ratio of combined signal, noise and distortion levels to the combined level of noise and distortion present in a system.

Signal to Noise (S/N)

The ratio of signal level to the level of noise present in a system, usually expressed in decibels.

Sinusoidal carrier

A fundamental waveform, characterized by a single frequency and wavelength, used to carry data or information by modulating some feature of the waveform.

Source Decoding

The process of recovering the original or source data from a received source encoded bit stream.

Source Encoding

The process of operating upon original or source data to produce an encoded message for transmission.

Spectrum Mask

The maximum power density of a transmission expressed as a function of frequency.

Spectrum – electromagnetic

The continuum of electromagnetic waves, distinguished by frequency components and bands that exhibit particular features or have been used for particular applications, including radio, microwave, ultraviolet, visual, infrared, X-rays and gamma rays.

Spectrum–signal

Expression used to denote the make-up of a signal or waveform in terms of sinusoidal components of different frequency and phase relationship (spectral components).

Spread Spectrum

Techniques for uniformly distributing or spreading the information content of a data carrying signal over a frequency range considerably larger than required for narrow band communication, allowing data to be recoverable under conditions of strong interference and noise.

Synchronization

The process of controlling the transmission of data using a separate or derived clocking signal.

Synchronous transmission

A method of data transmission that requires timing or clocking information in addition to data.

Tolerance

The maximum permissible deviation of a system parameter value, caused by any system or environmental influence or impact. Usually expressed in parts per million (ppm). Tolerances are specified for a number of radio frequency parameters, including carrier frequencies, sub-carriers, bit clocks and symbol clocks.

Vector

A quantitative component that exhibits magnitude, direction and sense.

Verification

The process of assuring that an intended operation has been performed.

Write

The process of transferring data to a transponder, the internal actions of storing the data, which may also encompass the reading of data to verify the data content.

Write Once Read Many (WORM)

Distinguishing a transponder that can be part or totally programmed once by the user, and thereafter only read.

Write Rate

The rate at which data is transferred to a transponder and stored within the memory of the device and verified. The rate is usually expressed as the average number of bits or bytes per second over which the complete transfer is performed.