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his article discusses the design
and modeling of both low
frequency (LF) and high frequency
(HF) RFID devices using CST®
STUDIO SUITE®. This can be done
at the level of the individual tag, but
also for the entire system, including
the reader, the tagged object and its
surroundings. Analyzing the entire
system with simulation allows the
suitability of the chosen RFID system
for the application to be investigated,
and can reveal unforeseen interactions
that can be hard to identify with
measurement alone.
Overview
Radio frequency identification (RFID)
makes it possible to catalogue, label
and track items quickly in demanding
environments. At the heart of all RFID
systems is the tag – an inductive coil
or antenna usually connected to a
small microchip. When interrogated
by an RFID reader, this chip generates
a unique data string which allows the
tag to be identified and, if necessary,
can provide additional information to
the reader.
Most RFID tags in common use are
passive, which means that they don’t
carry any power source. Instead, the
power to run the tag is supplied by
the interrogating reader through a
near-fi eld or far-field coupling to the
reader. This means that RFID can
be very sensitive to other objects in
the environment. Interference and
shielding effects can both affect
the performance of tags, and they
need to be taken into account when
considering an RFID system. Full-
wave EM simulation can capture
the behavior of RFID devices in
great detail, making it possible to
investigate how a tag will behave
without constructing a prototype.
Tag simulation
For the purposes of simulation, RFID
systems can be divided broadly
into two groups: low frequency
(frequencies up to tens of megahertz)
and high frequency (hundreds of
megahertz or greater). LF RFID
tags are very much smaller than the
wavelength of the reader field. They
act as an inductive coil, and couple
only through the magnetic field.
Common applications of LF RFID are
animal tagging, industrial process
control and smart card ticketing.
These applications do not typically
require high data rates, but do need
to be very robust.
Since they are electrically small, LF
T
RFID And Wireless Power transfer
simulation From Tag to system
Marc Rütschlin, CST AG
52 l New-Tech Magazine Europe