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Radio frequency identification [] (RFID), in the German technical literature occasionally radio operator identification, is contactless a method, in order data on a transponder and without visual contact reads and to store to be able. This transponder can be attached at objects, which can be identified and located then on the basis the data stored on it automatically and fast.
RFID is used as generic term for the complete technical infrastructure. A RFID system covers
The data communication between transponders and read receipt unit takes place at it by means of electromagnetic waves. With low frequencies this happens inductively over a near field, with higher over an electromagnetic far field. The distance, over which a RFID transponder can be selected, varies depending upon execution (passively/actively), frequency band, transmitting power used and environmental influences between few centimeters and more than one kilometer.
First RFID applications were used end of the Second World War. There the RFID technology served for the friend enemy recognition. In the airplanes and tanks transponders and Leseeinheiten were attached, in order to recognize whether the position which can be fired at or the approaching airplanes was to be attacked or not. Until today follow-up systems are used in the armies.
Into the 1970ern the first commercial forerunners were brought to the RFID technology on the market. It concerned thereby electronic goods security systems (English electronics Article Surveillance, EAS) with 1 bit storage capacity. By examination of the marking (available/is missing) theft should be reduced. The systems were based on microwave engineering or induction.
The year 1979 brought numerous new developments, and application type for the RFID technology. An emphasis was thereby on applications for the agriculture, as for example to animal marking.
The technology was promoted to the 1980ern particularly by the decision of several American Federal States as well as Norway to use RFID transponders in the traffic for Mautsysteme.
Into the 1990ern RFID technology was used common in the USA for Mautsysteme. Systems for access controls, paying by transfer, ski passports, followed tank maps, electronic going away barriers etc.
1999 were rung in with establishment of the car ID of center to WITH the development of a global standard for goods identification. With conclusion of the work to electronics the Product code (EPC) the car ID center was closed 2003. The results became simultaneous to the EPCglobal Inc. created again by uniform code Council (UCC) and EAN international (today GS1 US and GS1). handed over.
Transponders consist of:
For the size the antenna and the housing are relevant. The form and size of the antenna depends on the frequency and/or wavelength. Depending upon demanded application transponders in different designs, sizes and safety class systems are offered.
The picture shows a RFID chip above in a cheque card. From the chip left down two fine wires (green arrows) lead to a coil. It consists of many Drahtwicklungen and fills out nearly the entire size of the map.
RFID transponders know, depending upon operational area, quite the size of books possess (e.g. in container logistics). However it is also possible with today's technology to manufacture very small RFID transponders which can be begun in cash notes or paper.
Transponders are predominantly produced and used since beginning of the employment as LF 125kHz passive. ISOC POOL OF BROADCASTING CORPORATIONs, Card designs from the LF 125 kHz range world-wide the most frequently used designs are CLAMSHELL in the range admission control and time registration. Within the range E-PURSE (electronic purse and Ticketing) finds 13.56 MHz Mifare technology application and world-wide in many cities (Seoul, Moscow, London, Warsaw etc.) in undergrounds, penalties and as university and student document of identification is used. Transponders in the form of labels, which facilitate for example the medium safety device and posting in libraries, are only manufactured since the year 2000 in large numbers of items. Exactly the same exist also designs, which in the autokey are built (going away barrier), and/or as implants, Pansenboli or ear marks for the identification of animals serve. Further there is the possibility for the integration in nails or PU disk tags for pallet identification, in Chipcoins (account systems e.g. in public baths) or in smart cards (admission control).
The RFID transponders differ partly strongly from each other. The structure of a RFID transponder plans in principle an antenna, a similar circuit for receiving and sending (transponder), as well as a digital circuit and a permanent memory. The digital circuit is with more complex models an of Neumann architecture.
RFID transponders can have a several times recordable memory, in which during the life span information can be put down.
After area of application also other characteristic numbers differ like e.g. Radio frequency, data transmission rate, life span, costs per unit, storage location, reader calibration width and function range.
In principle RFID communication functions in such a way: The reader produces an electromagnetic (U) HF-field, which receives the antenna of the RFID transponder. In the antenna coil, as soon as it comes into the proximity of the electromagnetic field, induced current develops. This activates the microchip in the RFID day. With passive tags besides a condenser is loaded by the induced river, which provides for durable current supply of the chip. This takes over an inserted battery with active tags.
If that is once activated microchip, then it receives instructions from the reader. As the day modulates an answer into the field sent by the reader, it sends its serial number or other data queried by the reader.
The day does not send a field, but changed only the electromagnetic field of the reader through load modulation so mentioned, by using the energy of the field "", which again the reader detects. Principle-caused can be read 13.56 MHz a day therefore only in the electromagnetic near field, which has a range of the half wavelength, with 13.56 MHz thus maximally 11.1 meters.
In UHF range with 865 - the transponder antenna reflects or absorbs 920 MHz to same principle the electromagnetic field this, so that the relationship of the change of reflection of the reader can be noticed. One calls this Backscattering. Since water this radiation very strongly absorbed and metal reflects this radiation very strongly, is clearly that these materials affect this procedure very strongly, one day on these materials thus hardly readable is.
Since the power supply of the microchip must be covered with both procedures continuous (commercial UHF day with Phillips's chip after EPC 1,19 standard needs about 0.35 microamperes at river for the chip), must the reader a durable field produce. One calls this in UHF range therefore "Continuous Wave ". Due to the fact that the field strength decreases must this distance squarely with the distance and in both directions - from the reader to the day and back - be put back, this Continuous Wave must be quite high performance. Usually one uses EIRP here between 0,5 and 2 Watts.
This achievement would make at the reader all answers day bloomings and thus illegible. Therefore UHF answers day not in the frequency of the Continuous Wave, but in a sideband in such a way specified. As the day with a frequency of 200 kHz modulates an answer signal, it produces sidebands, which 200 kHz lie above and below these Continuous Wave. Thus these lie exactly in the adjacent channel from the ETSI specified radio regulation. These can be read by fading out the Continuous Wave in the reader problem-free.
For special's applications also cryptography modules or external sensors can e.g. being integrated like government inspection departments into the RFID transponder. Also the RFID send Empfangseinheiten differs in function range and appearance. Like that it is possible to integrate it directly in shelves or air-locks for persons (e.g. during the customs clearance).
The multiplicity of different devices and labels is only too much small part completely compatible. Regionally the used frequencies differ and preferred standards.
Besides it can come to problems, if the RFID transponder sits directly at the product and this a "high" density has. In order to go around this, in logistics among other things Flap or flag tags so mentioned is used, which rectangular from the product are away and so a large distance to the product have.
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