Fundamental Operating Principles - RFID: Fundamentals and Applications in Contactless Smart Cards and Identification - page 42

Figure 3.14 Different designs of inductively coupled transponders. The photo shows half fin-
ished transponders, i.e. transponders before injection into a plastic housing (reproduced by
permission of AmaTech GmbH & Co. KG, D-Pfronten)
Figure 3.15 Reader for inductively coupled transponder in the frequency range < 135 kHz with
integral antenna (reproduced by permission of easy-key System, micron, Halbergmoos)
0.16 λ , so that the transponder is located in the near field of the transmitter antenna
(for a more detailed definition of the near and far fields, please refer to Chapter 4).
If a resonant transponder (i.e. a transponder with a self-resonant frequency corre-
sponding with the transmission frequency of the reader) is placed within the magnetic
alternating field of the reader's antenna, the transponder draws energy from the mag-
netic field. The resulting feedback of the transponder on the reader's antenna can be