RFID介绍和协议

RFID BasicsIntroductionThe requirementInventory seems to be vanishing into thin air, or simply cannot be traced. You have to meet legal stipulations about the frequency w ith w hich your products are used, or you are interested in product life cycle. Sec urity is a must in your operations, and you w ant to know who has access to your premises -- w ithout bothersome issue and management of keys. The r ight control of material flow and monitor ing of manufacturing processes could mean huge cost savings. Front-to-end documentation of manufacturing processes is a quality management requirement. You w ould very much like to know w ho is using your w ork aids in case they are returned in poor shape. Goods acquisition in a matter of seconds -- precise and proof against manipulation. Theft and loss are words that you no longer w ant to see or hear in your bus iness vocabulary. Time and attendance r ecording -- accurate and reproducible w ithout tedious paperw ork. Fast recognition of product piracy and trademark counterfeiting so you can initiate counter measures. Immediate detection and analysis of product faults.The remedyCreate transparency and new know ledge through identity. Identity is usually understood as the sum of characteristics by w hich one individual or object can be distinguished from others.Smart tags make it possible to give an identity to persons or items, by infor mation that can be reproduced, expanded and evaluated. This means of assigning information allow s you to gain new findings, and immediately turn them into an economic benefit by taking the right decisions. Competitive advantages and cost savings are virtually guaranteed.The technologySmart tags or RFID labels assign any object a reproducible identity in the for m of a code that is uniqueworldw ide. Such a label may also hold additional infor mation like production data. Contactless trans mission of the data by w ireless w ill w ork reliably even w ithout line of sight, making this technology more flex ible and productive than conventional identification systems.cking and access applications during the 1980s.These w ireless AIDC systems (Automatic Identification and Data Capture) allow for non-contact reading and are effective in manufacturing and other hostile env ironments w here bar code labels could not surv ive.RFID has established itself in a w ide range of mar kets including livestoc k identification and automated vehic le identification (AVI) systems because of its ability to track moving objects.What is RFIDRFID stands for radio frequency identification. This technology allow s transmission of data w ithout contact and line of sight from a data medium, w hat is called a tr ansponder, to a reader and vice versa. The ter m transponder is for med from the tw o w ords transmitter and responder.The reader functions as a trans mitting and receiving unit, and produces an electromagnetic field. This is detected by the antenna of the tr ansponder and charges its energy storage mechanis m. As a result, the microchip contained in the transponder is activated and can receive commands from the reader through its antenna and also trans mit. When it responds, the transponder does not emit a magnetic field of its ow n, instead it modulates the magnetic field of the reader. This process is repeated for as long as the transponder and reader have a certain proximity to one another, or a connected system issues the appropriate command.History of developmentOver the years, the components of the system w ere further developed and applications expanded. In the 1970s for example, RFID w as already being used to identify railroad cars or automobile parts in paint shops. Shortly afterw ards electronic article surveillance appeared, the first large-scale system of its kind on the market. Its main purpose w as to guard against theft of goods and clothing. At the end of the 20th century use of RFID w as continuously expanding, into toll systems, subw ay tickets, as implants for animal identification and as an electronic immobilizer. The technology became know n to a w ide public a few years ago w hen largesuper mar ket concer ns decided to document the delivery chain of their goods by means of RFID. Since then there have been many reports on RFID in the media, and its use has also frequently been the subject of controversy.ElementsA conventional RFID system is made up of three components:a reader,an antennaa transponder (or tag) electronically programmed w ith unique data.TransponderThe nucleus of an RFID system is a data carrier -- the transponder or tag. It consists of a s mall chip and an antenna integrated in a package like a glass rod or an adhesive label. There is often a number, uniqueworldw ide, stored on the chip that is linked to information in a database. In the meantime ther e are also passive transponders w ith memory capac ity of up to 2 kbits, enabling extra information to be stored.The most common distinction made betw een transponders is how they are pow ered. They come in both passive and active versions.Passive transponders have no voltage supply of their ow n, and obtain their energy by creating an induction field by means of the radio signals of the reader. Although the lack of an energy source means shorter range, it does allow smaller and lighter components. Further more, passive transponders need no maintenance and cost much less. They are used pr imar ily for product authentification and tracking, and also as a data medium in access control systems. ctive transponders draw their energy from a built-in battery, so they can also send signals to trans mit data. Their integrated ener gy source makes them more expensive than passive counterparts, but on the other hand they have a reading range of up to 100 meters. Their main use is in the identification of objects w ith a long lifetime and that are often reused.Transponders are available in many different sizes, designs and safety clas ses depending on w hat they are intended for. Common forms are, in particular, adhesive labels or chip cards. There ar e read-only versions that, as the name implies, can only be read, and read/w rite versions that allow both reading and w riting of the transponder.AntennaAn RFID antenna consists of a coil w ith one or mor e w indings and a matching netw ork. It radiates the electromagnetic w aves generated by the reader, and receives the RF s ignals from the transponder. An RFID system can be designed so that the electromagnetic field is constantly gener ated, or activated by a sensor.Antennas also come in different sizes and designs, this depending very much on the environment into w hich a system is integrated. The required read and w rite range also play a role. Common for ms are r od or loop antennas. For gr eater reading range or different orientations of a transponder, a number of antennas can be arranged in one reader unit.ReaderDepending on the frequency that is used and its performance, an RFID reader sends radio w aves of betw een one centimeter and 30 meters or more. If a transponder enters this electromagnetic region, it detects the activating signal from the reader. The RFID reader decodes the data stored in the integrated circuit of the transponder (silicon chip), and communicates them, depending on the application, to a host system.The major ity of these devices can both read and w rite, so data transfer w ill also w ork in the reverse direction from the system to the data medium or tag.The reader is consequently the major component of the system, respons ible for activating the transponder and thus for initiating data communication.RFID readers are differentiated by their features, the main ones being stationary or mobile.Stationary devices are intended for firm incorporation in ex isting systems, and are the commonest type found. The necessary antenna is attached through an interface. Detected data can be conducted to a host on standard interfaces like RS232, E thernet or USB.Mobile readers serve for detecting data on var ious objects and are notable for their compactness. The antenna is integrated in the dev ice or directly attached to it. Data transfer to a host uses w ireless standards like W-LAN or DECT.StandardsGenerally it can be said that the development of standards is essential for cross-corporation and international use of new technologies. This also applies to RFID. Only standar dized products can communicate w ith one another across boundaries, and form the basis for netw orked systems.The major w orldw ide standardization bodies are the ISO (International Organization for Standardization) and EPCglobal (Electronic P roduct Code). The ISO is responsible for a variety of standards, regulating air interfaces, data protocols and applications for instance. The standard developed by EPCglobal is directed primar ily at trade, allocating different products a unique code similar to barcode. But the big advantage compared to barcode is that a single product of a series can be identified (e.g. a yoghurt tub) and that not just the series is classified.Her e is an overview of different RFID standards:Contactless SmartcardsISO 10373: test methods for smart car dsISO 10536: close coupling s mart cards (range up to 1 c m)ISO 14443: proximity coupling s mart cards (range up to 10 c m)ISO 15693: vicinity s mart cards (range up to 1 m)Container identification (logistics): ISO 10374Tier identificationISO 11784ISO 11785: FDX, HDX, SEQISO 14223: advanced transpondersTools: ISO 69873VDI 4470: anti-theft systems for goodsItem managementISO/IEC 18000Part 1: Reference architecture and definition of parameters to be standardizedPart 2: P ar ameters for air interface communications below 135 kHzPart 3: P ar ameters for air interface communications at 13.56 MHzPart 4: P ar ameters for air interface communicat ions at 2.45 GHzPart 6: P ar ameters for air interface communications at 860 MHz to 960 MHzPart 7: P ar ameters for active air interface communications at 433 MHz EPCglobal (Electronic P roduct Code。