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Radio Frequency Identification (RFID) is a wireless communications technology with which stationary or moving objects can be identified by magnetic or electromagnetic fields without requiring contact.

The technology is deployed in fields ranging from article surveillance and identification systems to contactless chip cards and personal and animal identification.

RFID systems basically consist of the following components:

  • a transponder (also known as a tag) which clearly identifies the objects by means of the data stored in it,
  • a reader capable of reading the data stored in the transponder, and
  • a computer which decodes and evaluates the data from the reader.

The transponder usually comprises an antenna and a microchip. Energy supply is either by passive means which implies that the transponder derives the energy it requires from the reader's environs or by active means via an integrated battery.

Readers consist of an RF unit (transmitter and receiver), a coupler (antenna) to the transponder and an interface to the evaluation device.

If a transponder strays into the vicinity of a reader, it is activated by the latter's field. The transponder subsequently modifies the reader's field in line with the data to be transmitted. The reader registers these field modifications and evaluates them.

The transmit frequencies used by most RFID devices are in the licence-exempt ISM bands (ISM = Industrial, Scientific, Medical). The readers' permissible magnetic field strengths are 66 dBμA/m (135 kHz) and 60 dBμA/m (13.56 MHz) at a distance of 10 metres. In the UHF range (868 MHz) a maximum transmitter power of 2 W ERP (Effective Radiated Power) is permitted, in the microwave range (2.45 GHz) a maximum transmitter power of 4 W ERP is permitted (in closed rooms). The range of RFID systems varies between a few millimetres (audio frequency range, passive transponder) and more than 10 m (microwave range, active transponder).


Date of modification: 2010.07.14

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