RFID
| Radio-frequency identification (RFID) uses electromagnetic fields to automatically identify and track tags attached to objects. An RFID system consists of a tiny radio transponder, a radio receiver and transmitter. When triggered by an electromagnetic interrogation pulse from a nearby RFID reader device, the tag transmits digital data, usually an identifying inventory number, back to the reader. This number can be used to track inventory goods. | |
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| wikipedia:: Radio-frequency identification |
uses electromagnetic fields to automatically identify and track tags attached to objects. An RFID system consists of a tiny radio transponder, a radio receiver and transmitter. When triggered by an electromagnetic interrogation pulse from a nearby RFID reader device, the tag transmits digital data, usually an identifying inventory number, back to the reader.
Passive tags are powered by energy from the RFID reader's interrogating radio waves.
Active tags are powered by a battery and thus can be read at a greater range from the RFID reader, up to hundreds of meters.
Tags
RFID tags are made out of three pieces:
- a micro chip (an integrated circuit which stores and processes information and modulates and demodulates radio-frequency (RF) signals)
- an antenna for receiving and transmitting the signal
- a substrate18(https://en.wikipedia.org/wiki/Radio-frequency_identification#cite_note-18).[[19]](https://en.wikipedia.org/wiki/Radio-frequency_identification#cite_note-constr-19)
Readers
RFID systems can be classified by the type of tag and reader. There are 3 types:22(https://en.wikipedia.org/wiki/Radio-frequency_identification#cite_note-22)
- A Passive Reader Active Tag (PRAT) system has a passive reader which only receives radio signals from active tags (battery operated, transmit only). The reception range of a PRAT system reader can be adjusted from 1–2,000 feet (0–600 m), allowing flexibility in applications such as asset protection and supervision.
- An Active Reader Passive Tag (ARPT) system has an active reader, which transmits interrogator signals and also receives authentication replies from passive tags.
- An Active Reader Active Tag (ARAT) system uses active tags activated with an interrogator signal from the active reader. A variation of this system could also use a Battery-Assisted Passive (BAP) tag which acts like a passive tag but has a small battery to power the tag's return reporting signal.
Fixed readers are set up to create a specific interrogation zone which can be tightly controlled. This allows a highly defined reading area for when tags go in and out of the interrogation zone. Mobile readers may be handheld or mounted on carts or vehicles.
Signaling
- Tags operating on LF and HF bands are, in terms of radio wavelength, very close to the reader antenna because they are only a small percentage of a wavelength away. In this near field region, the tag is closely coupled electrically with the transmitter in the reader. The tag can modulate the field produced by the reader by changing the electrical loading the tag represents. By switching between lower and higher relative loads, the tag produces a change that the reader can detect.
- At UHF and higher frequencies, the tag is more than one radio wavelength away from the reader, requiring a different approach. The tag can backscatter a signal.
- Active tags may contain functionally separated transmitters and receivers, and the tag need not respond on a frequency related to the reader's interrogation signal.