Introduction - RFID: Fundamentals and Applications in Contactless Smart Cards and Identification - page 9

Figure 1.8 RFID reader and contactless smart card in practical use (reproduced by permission
of Kaba Benzing GmbH)
Coupling element (coil, antenna)
Housing
Chip
Figure 1.9 Basic layout of the RFID data-carrying device, the transponder. Left, inductively
coupled transponder with antenna coil; right, microwave transponder with dipolar antenna
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.