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Numerical analysis of wireless power transfer in near-field UHF-RFID systems

Published online by Cambridge University Press:  27 November 2017

Alice Buffi*
Department of Information Engineering, University of Pisa, Via G. Caruso 16, IT-56122 Pisa, Italy. Phone: +39 050 2217 576
Andrea Michel
Department of Information Engineering, University of Pisa, Via G. Caruso 16, IT-56122 Pisa, Italy. Phone: +39 050 2217 576
Paolo Nepa
Department of Information Engineering, University of Pisa, Via G. Caruso 16, IT-56122 Pisa, Italy. Phone: +39 050 2217 576
Giuliano Manara
Department of Information Engineering, University of Pisa, Via G. Caruso 16, IT-56122 Pisa, Italy. Phone: +39 050 2217 576
Corresponding author: A. Buffi Email:


A preliminary numerical analysis of the power transfer efficiency (PTE) for the forward link of near-field (NF) ultra high frequency (UHF)-radio frequency identification (RFID) systems is addressed in this paper, by resorting to an impedance matrix approach where the matrix entries are determined through full-wave simulations. The paper is aimed to quantify the NF-coupling effects on the PTE, as a function of the distance between the reader and tag antennas. To allow for a PTE comparison between different reader and tag antenna pairs, a benchmarking tag-loading condition has been assumed, where the tag antenna is loaded with the impedance that maximizes the PTE. In a more realistic loading condition, the load impedance is assumed as equal to the conjugate of the tag antenna input impedance. Full-wave simulations use accurate antenna models of commercial UHF-RFID passive tags and reader antennas. Finally, a “shape-matched antenna” configuration has been selected, where the reader antenna is assumed as identical to the tag antenna. It is shown that the above configuration could be a valuable compact solution, at least for those systems where the relative orientation/position between the tag and reader antennas can be controlled, and their separation is of the order of a few centimeters or less.

Wirelessly Powering: The Future
Copyright © Cambridge University Press 2017 

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