use of radio frequency electromagnetic fields to transfer data, for the purpose of automatically identifying and tracking tags attached to objects.
The tags contain electronically stored information. Some tags are powered and read at short ranges by magnetic fields. Others are powered by a local power source such as a battery, or in some cases they don’t have a battery but collect energy from the interrogating EM field, and then act as a passive transponder to emit microwaves or UHF radio waves.
RFID tags are used in several different industries. They can be attached to an automobile during production and can be used to track its progress through the assembly line. Additional RFID applications include, pharmaceuticals which can be tracked through warehouses, during deliveries and when they have reached their destination. Livestock and pets may have tags injected, allowing positive identification of the animal. RFID tags can also be used to save lives when they are used on offshore oil and gas platforms. The tags are worn by personnel as a safety measure, allowing them to be located 24 hours a day and to be quickly found in emergencies.
The RFID chip’s information is stored electronically in a non-volatile memory. The tag includes a small RF transmitter and receiver. An RFID reader transmits an encoded radio signal to interrogate the tag. The tag receives the message and responds with its identification information, which may only be a unique serial number or it may even be product related information such as a stock number, lot or batch number, production date, or other product specific information.
RFID systems can be classified by the type of tag and reader they require. A Passive Reader Active Tag (PRAT) system has a passive reader which only receives radio signals from active tags. The reception range of a PRAT system reader can be adjusted from 1-2,000 feet, 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 that is initiated with an interrogator signal from an 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.
Readers that are fixed in place can be setup to create a specific interrogation zone which can be tightly controlled. This allows a highly targeted reading area for when the tags go in and out of the interrogation zone.
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