RFID Systems
RFID systems are closely related to the smart cards described above. Like smart card systems, data is stored on an electronic data-carrying device – the transponder. However, unlike the smart card, the power supply to the data-carrying device and the data exchange between the data-carrying device and the reader are achieved without the use of galvanic contacts, using instead magnetic or electromagnetic fields. The underlying technical procedure is drawn from the fields of radio and radar engineering. The abbreviation RFID stands for radio frequency identification, i.e. information carried by radio waves.

Due to the numerous advantages of RFID systems compared with other identification systems, RFID systems are now beginning to conquer new mass markets. One example is the use of contactless smart cards as tickets for short-distance public transport.

A Comparison of Different ID Systems
A comparison between the identification systems described above highlights the strengths and weakness of RFID in relation to other systems (Table 1.2). Here too, there is a close relationship between contact-based smart cards and RFID systems; however, the latter circumvent all the disadvantages related to faulty contacting (sabotage, dirt, unidirectional insertion, time-consuming insertion, etc.).

Components of an RFID System
An RFID system is always made up of two components:
the transponder, which is located on the object to be identified;
the interrogator or reader, which, depending upon the design and the technology used, may be a read or write/read device (in this book – in accordance with normal colloquial usage – the data capture device is always referred to as the reader, regardless of whether it can only read data or is also capable of writing).

A reader typically contains a radio frequency module (transmitter and receiver), a control unit and a coupling element to the transponder. In addition, many readers are fitted with an additional interface (RS 232, RS 485, etc.) to enable them to forward the data received to another system (PC, robot control system, etc.).

The transponder, which represents the actual data-carrying device of an RFID system, normally consists of a coupling element and an electronic microchip. When the transponder, which does not usually possess its own voltage supply (battery), is not within the interrogation zone of a reader it is totally passive. The transponder is only activated when it is within the interrogation zone of a reader. The power required to activate the transponder is supplied to the transponder through the coupling unit (contactless), as are the timing pulse and data.