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Efficient Antenna Design of Inductive Coupled RFID-Systems with High Power Demand

Christian Reinhold1,2, Peter Scholz1,2, Werner John2, Ulrich Hilleringmann1,
1. University of Paderborn, Department of Electrical Engineering, Sensor Technology Group, Germany
2. Fraunhofer IZM, Departement Advanced System Engineering, Paderborn, Germany

Abstract—In contrast to pure identification labels, passiveinductive coupled RFID transponders with enhanced functionalityhave an increased power consumption. A nonoptimizedantenna design for high power transponders maylead to a poor efficiency and high magnetic field emissions.Therefore, in this work, the energy transmission of inductivecoupled systems is investigated, enabling an optimizedsystem design. The RFID system is modeled by networkelements in order to optimize the energy transmission. Nextto a brief review of different methods for the antennaparameter determination, a new modification of the PEECmethod is derived enabling an accelerated and accuratecomputation of the mutual coupling of the reader and thetransponder antenna. Along with the simplification of thetransformed transponder impedance and the investigation ofthe reader matching, consecutive design steps are deduced.The influence of the location-dependent antenna couplingon the energy transmission is characterized. Two casestudies are carried out showing a successful transmissionof 80mW over a distance of up to 7.6 cm by 275mW readeroutput power. This system demonstrates an efficient energysupply of a high power transponder while keeping the fieldemissions low.

Index Terms—RFID System, Antenna Design, InductiveCoupling, Wireless Energy Transmission, Quality Factor,Inductance Calculation, PEEC

Cite: Christian Reinhold, Peter Scholz, Werner John, and Ulrich Hilleringmann, "Efficient Antenna Design of Inductive Coupled RFID-Systems with High Power Demand," Journal of Communications, vol. 2, no. 6, pp. 14-23, 2007.