RFID tags
can be as thin as a dollar bill.
Radio Frequency Identification, or RFID, is a wireless technology used to track and identify an object via radio wave signals. In most cases, RFID tags or chips are either embedded into or attached to an object. Target objects can range from living organisms, such as RFID tags clipped to the ears of cattle, to consumer items such as clothing and electronics. Since the late 1990s, some governments have been using RFID chips built into passports and other personal identification documents.
Basic Construction
A working RFID system includes a tag, antenna and reader. The RFID tag, which includes the RFID chip, is the device attached to the object. Tags can be a variety of shapes and sizes, from slim labels to large strengthened boxes. The tag is made of a circuit which stores information and generates a radio signal, and an antenna that transmits that signal to the reader.
Identification Chip
Within each RFID tag is a microchip, often no larger than a couple of grains of rice. It is this microchip that contains the identification data---in the form of a unique serial number. The chip acts as an integrated circuit able to create electric current when activated. According to the International Journal of Computer Science, a chip can be either permanently fixed with the same information or have the ability to be rewritten with a new ID.
Transmitting the ID
While the microchip stores the unique ID data, it requires a means to transmit that information. The antenna translates the frequency emitted by the chip and then transmits that to a reader. If either the chip or the antenna is damaged, then the RFID tag is effectively out of action, as it cannot communicate with the reader.
Passive and Active
According to a Massachusetts Institute of Technology paper referenced by the Harvard Computer Science Department, there are three main types of RFID tag---passive, semi-passive and active. Passive tags are only activated when receiving a signal from an external reader. These are often used for store items. Semi-passive tags contain a limited power source, and may only become operational when a signal is received from a reader. Active RFID tags have their own in-built power source and can send signals without external activation. These are often used for more expensive items, such as shipping containers.
Range
The range of an RFID transmitter varies according to the type of tag. Passive tags may only be able to transmit data within 30 feet. Active tags may have a range of up to 320 feet or more, depending on the strength of the battery and the transmitter.
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