rfid常用术语.pdf

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1、RFID 常用术语 1-1 RFID 常用术语 RFID 常用术语（摘自 RFID JOURNAL 网站）A Active tag:An RFID tag that has a transmitter to send back information,rather than reflecting back a signal from the reader,as a passive tag does.Most active tags use a battery to transmit a signal to a reader.However,some tags can gather energy

2、 from other sources.Active tags can be read from 300 feet(100 meters)or more,but theyre expensive(typically more than US$20 each).Theyre used for tracking expensive items over long ranges.For instance,the U.S.military uses active tags to track containers of supplies arriving in ports.Addressability:

3、The ability to write data to different fields,or blocks of memory,in the microchip in an RFID transponder.Agile reader:A generic term that usually refers to an RFID reader that can read tags operating at different frequencies or using different methods of communication between the tags and readers.A

4、ir Interface Protocol:The rules that govern how tags and readers communicate.Alignment:See Orientation.American National Standards Institute:An American technical standards body and the representative of the United States to the International Organization for Standardization.Amplitude:The maximum ab

5、solute value of a periodic curve measured along its vertical axis(the height of a wave,in laymans 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 stri

6、ng 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 RFID 常用术语 2-2 communicate data stored on a tag.ANSI:See American N

7、ational Standards Institute Antenna:The tag antenna is the conductive element that enables the tag to send and receive data.Passive,low-(135 kHz)and high-frequency(13.56 MHz)tags usually have a coiled antenna that couples with the coiled antenna of the reader to form a magnetic field.UHF tag antenna

8、s can be a variety of shapes.Readers also have antennas which are used to emit radio waves.The RF energy from the reader antenna is harvested by the antenna and used to power up the microchip,which then changes the electrical load on the antenna to reflect back its own signals.Antenna gain:In techni

9、cal terms,the gain is the ratio of the power required at the input of a loss-free reference antenna to the power supplied to the input of the given antenna to produce,in a given direction,the same field strength at the same distance.Antenna gain is usually expressed in decibels and the higher the ga

10、in the more powerful the energy output.Antennas with higher gain will be able to read tags from farther away.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 mo

11、re than one tag in the same readers field.Association for Automatic Identification and Mobility:A global trade association for companies that provide products and services related to automatic identification,data collection,networking and information management systems.Attenuation:The reduction of e

12、nergy.See signal attenuation.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 into heat.Authentication:The veri

13、fication of the identity of a person,object or process.In RFID,the term is used in two ways.For contactless smart cards and other payments systems,the reader must make sure the transponder is a valid device within the system.That is,someone is not using an unauthorized device to commit fraud.There i

14、s also some RFID 常用术语 3-3 talk of using EPC technology to authenticate products as a way of reducing counterfeiting.Auto-ID Center:A non-profit collaboration between private companies and academia that pioneered the development of an Internet-like infrastructure for tracking goods globally through t

15、he use of RFID tags carrying Electronic Product Codes.The center closed its doors in September 2003.EPCglobal was set up to continue the work of commercializing EPC technology,and the centers research work is carried on by Auto-ID Labs at universities around the world.Auto-ID Labs:Nonprofit research

16、 labs,headquartered at the Massachusetts Institute of Technology,which continue to do primary research into the development of EPC and related technologies.Automatic Identification:A broad term that covers methods of collecting data and entering it directly into computer systems without human involv

17、ement.Technologies normally considered part of auto-ID include bar codes,biometrics,RFID and voice recognition.Automatic identification and data capture:A broad term that covers methods of identifying objects,capturing information about them and entering it directly into computer systems without hum

18、an involvement.Technologies normally considered part of auto-ID include bar codes,biometrics,RFID and voice recognition.B Backscatter:A method of communication between passive tags(ones that do not use batteries to broadcast a signal)and readers.RFID tags using backscatter technology reflect back to

19、 the reader radio waves from a reader,usually at the same carrier frequency.The reflected signal is modulated to transmit data.Bar code:A standard method of identifying the manufacturer and product category of a particular item.The bar code was adopted in the 1970s because the bars were easier for m

20、achines to read than optical characters.The main drawbacks of bar codes main are they dont,in most cases,identify unique items and scanners have to have line of sight to read them.Base station:An RFID reader that is connected to a host system.RFID 常用术语 4-4 Battery-assisted tag:These are RFID tags wi

21、th batteries,but they communicate using the same backscatter technique as passive tags(tags with no battery).They use the battery to run the circuitry on the microchip and sometimes an onboard sensor.They have a longer read range than a regular passive tag because all of the energy gathered from the

22、 reader can be reflected back to the reader.They are sometimes called semi-passive RFID tags.Beacon:An active or semi-active RFID tag that is programmed to wake up and broadcast its signal at a set intervals.C Card operating system:The software program stored in the smart card IC,which manages the b

23、asic functions of the card,such as communication with the terminal,security management and data management in the smart card file system.Carrier frequency:A frequency used to transmit data.Central processing unit:The brains of a computer,which controls all the other parts of the computer.Checksum:A

24、code added to the contents of a block of data stored on an RFID microchip that can be checked before and after data is transmitted from the tag to the reader to determine whether the data has been corrupted or lost.The cyclic redundancy check is one form of checksum.Chipless RFID tag:An RFID tag tha

25、t doesnt depend on a silicon microchip.Some chipless tags use plastic or conductive polymers instead of silicon-based microchips.Other chipless tags use 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 fin

26、gerprint to identify the object with the tag.Companies are experimenting with embedding RF reflecting fibers in paper to prevent unauthorized photocopying of certain documents.Chipless tags that use embedded fibers have one drawback for supply chain usesonly one tag can be read at a time.Circular-po

27、larized antenna:A UHF reader antenna that emits radio waves in a circular pattern.These antennas are used in situations where the orientation of the tag to the reader cannot be controlled.RFID 常用术语 5-5 Since the waves are moving in a circular pattern,they have a better chance of hitting the antenna,

28、but circular-polarized antennas have a shorter read range than linear-polarized antennas.Closed-loop systems:RFID tracking systems set up within a company.Since the tracked item never leaves the companys control,it does not need to worry about using technology based on open standards.Collaborative p

29、lanning,forecasting and replenishment:A general term used to describe cooperation between manufacturers and retailers to better match supply of goods with demand for them.Commissioning a tag:This term is sometime used to refer to the process of writing a serial number to a tag(or programming a tag)a

30、nd associating that number with the product it is put on in a database.Compatibility:Two RFID systems are considered compatible if they use the same protocols,frequencies and voltage levels and are able to operate together within the same overall application(see interoperability).Concentrator:A devi

31、ce connected to several RFID readers to gather data from the readers.The concentrator usually performs some filtering and then passes only useful information from the readers on to a host computer.Conducted Power:Conducted power is the RF power that is supplied by an RFID system to the antenna.Typic

32、ally,it is calculated or measured at the cable to antenna connection.In the United States,Federal Communication Commission regulations require a maximum conducted power of 1 Watt.Conductor:A material,such as aluminum and copper,which readily conducts electricity.Conductors have a significant impact

33、on the performance of RFID tags.Conductors near tags can reflect RF energy in a way that reduces tag performance,and they can also detune the tag.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

34、be swiped through a reader.Such cards can speed checkout,providing consumers with more convenience.COS:See card operating system RFID 常用术语 6-6 Coupling:See inductive coupling.CPFR:See collaborative planning,forecasting and replenishment CPU:See central processing unit CRC:See cyclic redundancy check

35、 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.Cyclic redundancy check:A method of checking data stored on an RF

36、ID tag to be sure that it hasnt been corrupted or some of it lost.(See Checksum.)D Data carrier:A medium that holds machine-readable data.Bar codes and RFID tags are types of data carriers.The term is also applied to a carrier frequency used to transmit data.Data field:An area of memory in RFID micr

37、ochips that is assigned to a particular type of information.Data fields may be protected(see below)or they may be written over,so a data field might contain information about where an item should be sent.When the destination changes,the new information is written to the data field.Data field protect

38、ion:The ability to prevent data stored in a specific area of memory of an RFID microchip from being overwritten.Companies might want to protect the data field that stores an Electronic Product Code,which doesnt change during the life of the product its associated with.Data retention:The ability of a

39、 microchip to maintain the information stored in EEPROM.RFID tags and other microchips can typically retain data for 10 years or more,but data retention depends on temperature,humidity and other factors.Data transfer rate:The number of characters that can be transferred from an RFID tag to a reader

40、within a given time.Baud rates are also RFID 常用术语 7-7 used to quantify how fast readers can read the information on the RFID tag.This differs from read rate,which refers to how many tags can be read within a given period of time.dBi:The gain of an antenna compared to an isotropic antennathat is,an a

41、ntenna that radiates energy equally in every direction.A typical dipole antenna has a dBi of 2.2 when compared to an isotropic antenna.dBm:See decibel dBw:Decibels(dB)referenced to 1.0 watt.Using the decibel formula:dB=10 log(P1/P2),P2 equals 1.0 watt and P1 is in units of watts.De-tune:UHF antennas

42、 are tuned to receive RFID waves of a certain length from a reader,just as the tuner on the radio in a car changes the antenna to receive signals of different frequencies.When UHF antenna is close to metal or metallic material,the antenna can be detuned,resulting in poor performance.Decibel:A unit u

43、sed to express the ratio between two values,including antenna gain,cable losses and reader power output.The formula for decibel is:dB=10 log(P1/P2).In laymans terms,dB represents the difference in the intensity of an emitted signal or power where 0 dB is the reference,3 dB is twice the intensity of

44、0 dB,10 dB is 10 times the intensity,and 20 dB is 100 times the intensity and so on.(See also dBi,dBm and dBw.)Detune:UHF antennas are tuned to receive RFID waves of a certain length from a reader,just as the tuner on the radio in a car changes the antenna to receive signals of different frequencies

45、.When UHF antenna is close to metal or metallic material,the antenna can be detuned,resulting in poor performance.Die:The silicon block onto which circuits have been etched to create a microchip.Dielectric constant:The measure of a materials ability to store a charge when an electric field is applie

46、d,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).Waters dielectri

47、c constant changes:At room temperature it is 80;near boiling RFID 常用术语 8-8 it is 55;and when frozen it is 3.2.Digital certificate:A digital message that contains the identity of an company or organization,its public key combined and a signature of this data from a certificate authority(Trust Center)

48、proving the correctness of this data.Digital signal processor:As special kind of microprocessor that converts changes in analog waves into digital information.DSPs are used in RFID readers.Digital signature:A cryptographic protocol that ensures the authenticity as well as the integrity of digital da

49、ta.A digital signature typically is realized by encrypting the hash value of the data to be protected with the private key.Digital signature algorithm:A cryptographic algorithm approved by the United States government for use in creating digital signatures.Dipole:An antenna made of two straight elec

50、trical conductors(poles).In an RFID transponder,these are connected to a microchip.The antenna is typically 1/2 wavelength from end to end.DSP:See digital signal processor Dual dipole:An antenna that has two dipoles.In an RFID transponder,these are attached to a chip.The dual dipole design greatly r