Differentiation Features of RFID Systems - RFID: Fundamentals and Applications in Contactless Smart Cards and Identification - page 22

capacitive (electric) coupling (motorola Inc., 1999). At least 90% of all RFID sys-
tems currently sold are inductively coupled systems. For this reason there is now an
enormous number of such systems on the market. There is also a series of standards
that specify the technical parameters of transponder and reader for various standard
applications, such as contactless smart cards, animal identification or industrial automa-
tion. These also include proximity coupling (ISO 14443, contactless smart cards )and
vicinity coupling systems (ISO 15693, smart label and contactless smart cards). Fre-
quencies below 135 kHz or 13.56 MHz are used as transmission frequencies. Some
special applications (e.g. Eurobalise) are also operated at 27.125 MHz.
RFID systems with ranges significantly above 1 m are known as long-range sys-
tems . All long-range systems operate using electromagnetic waves in the UHF and
microwave range . The vast majority of such systems are also known as backscatter
systems due to their physical operating principle. In addition, there are also long-range
systems using surface acoustic wave transponders in the microwave range. All these
systems are operated at the UHF frequencies of 868 MHz (Europe) and 915 MHz (USA)
and at the microwave frequencies of 2.5 GHz and 5.8 GHz. Typical ranges of 3 m can
now be achieved using passive (battery-free) backscatter transponders, while ranges
of 15 m and above can even be achieved using active (battery-supported) backscatter
transponders. The battery of an active transponder, however, never provides the power
for data transmission between transponder and reader, but serves exclusively to supply
the microchip and for the retention of stored data. The power of the electromagnetic
field received from the reader is the only power used for the data transmission between
transponder and reader.
In order to avoid reference to a possibly erroneous range figure, this topic uses
only the terms inductively or capacitively coupled system and microwave system or
backscatter system for classification.
2.4 Information Processing in the Transponder
If we classify RFID systems according to the range of information and data processing
functions offered by the transponder and the size of its data memory, we obtain a broad
spectrum of variants. The extreme ends of this spectrum are represented by low-end
and high-end systems (Figure 2.17).
2.4.1 Low-end systems
EAS systems (Electronic Article Surveillance systems ; see Section 3.1) represent the
bottom end of low-end systems . These systems check and monitor the possible presence
of a transponder in the interrogation zone of a detection unit's reader using simple
physical effects.
Read-only transponders with a microchip are also classified as low-end systems.
These transponders have a permanently encoded data set that generally consists only
of a unique serial number (unique number) made up of several bytes. If a read-only
transponder is placed in the HF field of a reader, the transponder begins to continuously