Industry Automation and Drive Technologies - SCE
TIA Training Document
Page 9 of 65
Module E11
Status: 01/2010 Radio Frequency Identification (RFID) with SIMATIC S7-300F-2PN/DP and
RF180C
4 RFID FUNDAMENTALS
Radio Frequency Identification (RFID) makes it possible to automatically identify and localize
objects and living beings, and thus considerably facilitates recording and storing data. The RFID
system consists of the following: 1) a transponder that is located in the object or in the living being
and identifies it, and 2) a reading device for reading out the transponder ID. The reading device
includes a software (a micro-program) that controls the actual read process, and an RFID
middleware with interfaces to other EDP systems and data bases.
As a rule, a read device generates an electro-magnetic high frequency field with a short range,
preferably with induction coils. It is not only used to transmit data, but to also to supply the
transponder with power. Only if larger ranges are to be obtained are active transponders used that
have their own power supply. Usually, the frequency of 13.56 MHz is used (RF300, ISO). The reading
device (reader) generates a high frequency electromagnetic alternating field that illuminates the aerial
of the RFID transponder (RFID tag). As soon as the aerial coil enters the electro-magnetic field, an
induction current is generated in it. This current is rectified, and with it, a capacitor is loaded as short
time storage which, for the read process, provides for the power supply of the chip. For active tags,
an installed battery takes care of the supply. The micro-chip thus activated in the RFID tag decodes
the commands sent by the reader. This reader encodes and modulates the reply into the irradiated
electro-magnetic field through field weakening in the contact-free short circuit, or in opposition
reflection of the field that the reader transmitted. With this, the tag transmits its own unchangeable
serial number, additional numbers of the marked object, or other data that the reader polled. The
transponder itself does not transmit a field; it only changes the reader’s electro-magnetic
transmission field.
Transponder switch open, aerial is on "Absorption“ (return value 0).
Transponder switch closed, aerial is on "Reflect“, (return value 1).
(Source: Wikipedia)
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