Effect of added resonators in RFID system at 13.56 MHz

• Published in: IET microwaves, antennas & propagation antennas & propagation, 2018-04, Vol.12 (5), p.684-691
• Main Authors: Benamara, Megdouda, Grzeskowiak, Marjorie, Diet, Antoine, Conessa, Christophe, Lissorgues, Gaëlle, Le Bihan, Yann
• Format: Article
• Language: English
• Subjects: added resonator effect; analytical formulation; coils; Electronics; Engineering Sciences; equivalent impedance matrix parameters; equivalent input impedance; frequency 13.56 MHz; frequency shift; HF antennas; impedance matrix; load modulation; Micro and nanotechnologies; Microelectronics; mutual inductance; optimisation; Other; radiofrequency identification; radiofrequency identification system tracking; reader antenna; reader coil; reader prototype; resonator positioning optimisation; resonators; RFID system; RFID system tracking; small commercial tag; small moving tag detection; Special Issue: Selected papers from the Loughborough Antennas & Propagation Conference (LAPC 2016); tag misalignment
• ISSN: 1751-8725; 1751-8733; 1751-8733
• DOI: 10.1049/iet-map.2017.0500

In this study, a reader antenna including resonators is proposed to improve detection of a small moving tag in the case of tracking a radiofrequency identification (RFID) system. The near-field RFID technology is based on load modulation, the input impedance on the reader coil and the mutual inductance between the reader and tag coils are the main parameters for performing detection. They are calculated from the impedance matrix parameters. The added resonators change all the parameters of the impedance matrix consequently the input impedance and mutual inductance are also changed. In this study, analytical formulation defining the equivalent impedance matrix parameters is developed. These formulae are used to evaluate the performance of the proposed design according to the tag misalignment (lateral and angular). From the calculation and simulation results, a frequency shift in the equivalent input impedance is found. To avoid this problem, optimising the positioning of the resonators on the reader coil is performed. This study is confirmed by measures of RFID detection for a reader prototype (with and without resonators) and a small commercial tag. Both the surface and volume of detection of the small moving tag (lateral and angular misalignment) are improved by the principle of added resonators.