New-Tech Europe | March 2016 | Digital edition

RFID And Wireless Power transfer simulation From Tag to system

Marc Rütschlin, CST AG

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his article discusses the design and modeling of both low

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

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

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