Fundamental Operating Principles - RFID: Fundamentals and Applications in Contactless Smart Cards and Identification - page 57

Dipole antenna
Interdigital transducer
Reflector
Piezoelectric single crystal
Figure 3.30 Basic layout of an SAW transponder. Interdigital transducers and reflectors are
positioned on the piezoelectric crystal
Figure 3.31 Surface acoustic wave transponder for the frequency range 2.45 GHz with antenna
in the form of microstrip line. The piezocrystal itself is located in an additional metal housing
to protect it against environmental influences (reproduced by permission of Siemens AG, ZT
KM, Munich)
and returned pulse sequence thus corresponds with the transmission frequency of the
sampling pulse.
Part of the surface wave is reflected off each of the reflective strips that are dis-
tributed across the substrate, while the remaining part of the surface wave continues
to travel to the end of the substrate and is absorbed there.