Matching approach for UHF RFID tag antenna immersed in dielectric materials
Introduction
In recent years, radio frequency identification (RFID) has become very popular in many applications domains, such as purchasing and distribution logistics, manufacturing companies and material flow systems. That provides wirelessly information about different items [1]. The adoption of this technology is not only limited to these application domains but it is greatly used with sensors to collect physical information about different items [2]. The large-scale implementation of the RFID technology revolutionized also the Internet of Things (IoT) [3], [4], [5].
In RFID technology, the transponders “tags” can be classified in two main categories: active (with power supply) or passive (no power supply) [6]. The active tags need power survey in order to ensure it function while passive tags exploit only the radio frequency energy radiated by transceiver. These latter communicate with the base station (reader) using a specific operating frequency. Each country adopts one special frequency band for RFID technology [7]. The repartition of the Ultra High Frequency (UHF) band is as follows: 866–869 MHz in Europe, 902–928 MHz in North and South America, and 950–956 MHz in Japan and some others Asian countries. A typical passive RFID tag is composed of two key elements: an antenna and an application specific integrated circuit (ASIC) chip [8].
A passive RFID system operates in the following way (see Fig. 1). A reader antenna transmits a query signal which is captured by the tag antenna. The radio frequency (RF) voltage established on tag antenna is converted to direct current [9]. This voltage activates the chip, and then the tag sends data back by varying its input impedance. The impedance usually switches between two different states: conjugate match and some other impedance values. That successfully modulates the back-scattered signal [9]. The RFID system does not need line-of-sight to collect information about interrogated items [10], [11]. Therefore, an RFID tag can be embedded into objects.
Most of RFID antenna do not work correctly when embedded in highly dielectric medias. Because the antenna was designed to match a specific ASIC chip impedance and tested in ideal conditions. However, the medium where antenna is embedded changes drastically the input impedance of the antenna. Generally, to develop a robust RFID system for automotive tire, there are two essentials challenges [11]. The first one is reliability and efficiency of the RF link between the tag and reader. The second one relates to tag’s structural persistence and durability. Further, the tag antenna must have the following performances: (i) compact size to be attached to the required objects; (ii) omnidirectional radiation patterns; (iii) good impedance matching; (iv) be robust to endure the mechanical effects caused by the tire while moving; (v) be cheap.
In passive RFID tag, the antenna should be self-resonant [12]. Therefore the matching circuit is integrated on antenna design to ensure low cost, low profile and maximum transmitted power between tags and reader. It is worth noting that ASIC chip has a complex impedance in terms of real and imaginary part. However ensuring proper impedance match is a challenging step.
In this work, we present a UHF RFID tag antenna designed for automotive tire. The size reduction technique is performed by using a meander line, whereas impedance matching is investigated in free space and in rubber media based on our approach. Besides, antenna shape and used materials are appropriate for low cost fabrication. The rest of this paper is structured as follows. Section 2 discusses our design methodology that led us to design the antenna, while Section 3 presents the results and discusses the performances of the proposed antenna. Finally, Section 4 offers a brief conclusion.
Section snippets
Size reduction
One of the most used methods to reduce antennas size is meandering (see Fig. 2). This technique has been widely implemented in RFID system to minimize the overall tag size. It is an attractive choice for size reduction purpose. Folding the elements in a meander produces resonances at much lower frequencies than the case of straight antenna element of identical length [12]. Because in a meandered line, adjacent vertical segment produces a wire configuration with both capacitive and inductive
Results and discussion
We aim to embed the tag in tire’s sidewall that has according to Grosinger et al. [16] study. With a view to validating our approach, we simulated the tag antenna in two different mediums: in free space and in rubber material. The piece of rubber has the following dimensions: length width and thickness . Fig. 5 depicts the simulated S11 parameter of both cases. We can notice that rubber medium affects the antenna input impedance and then changes the
Conclusion
A novel passive RFID tag antenna for automotive tire was proposed. The simulation results prove that our designed antenna will ensure good performances for automotive tire application and it can be a good candidate for RFID system. The meandering technique was a helpful solution to reduce the antenna size. The proposed approach was a efficient solution to predict the matching parameters when tag is embedded in rubber tire with high dielectric permittivity in order to maximize power delivered to
CRediT authorship contribution statement
Nadir Sarsri: Conceptualization, Methodology, Software, Data curation, Writing - original draft, Writing - review & editing. Sami Myllymäki: Visualization, Investigation, Resources. Marko Sonkki: Visualization, Investigation, Resources, Writing - review & editing. Mohamed Nabil Srifi: Supervision, Software, Validation, Writing - review & editing.
Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgment
Authors would like to thank Professor Jantunen Heli and all Microelectronics research unit team for the help on antenna design and measurements. Author acknowledge the financial support of the erasmus + program, Key 1 - Mobility for learners and staff - for the cooperation between Microelectronics research unit, University of Oulu, Finland, and Ibn Tofail University, Electronics and Telecommunication systems research unit, Morocco.
Nadir Sarsri received his engineering Degree in 2010, from National Institute of Posts and Telecommunications in Rabat, Morocco. He is currently a PhD student at Electronics and Telecommunication Systems Research Group, at National School of Applied Sciences (ENSA) in Kenitra. His research focus is RFID antenna design for automotive applications.
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Nadir Sarsri received his engineering Degree in 2010, from National Institute of Posts and Telecommunications in Rabat, Morocco. He is currently a PhD student at Electronics and Telecommunication Systems Research Group, at National School of Applied Sciences (ENSA) in Kenitra. His research focus is RFID antenna design for automotive applications.
Sami Myllymäki, born 1974 in Oulu, Finland, received the M.Sc. degree in microelectronics from the University of Oulu, in 1999, and the D.Sc. degree in electronic materials and components from the same University in 2012. He is currently adjunct professor and team leader at the University of Oulu focusing on radio and microwave frequency components and systems for telecommunications and sensor applications.
Marko Sonkki received his Master’s degree (M.Sc.) in Electrical Engineering from the Department of Electrical and Information Engineering at the University of Oulu, Finland, in 2004. In 2013, he received his D.Sc. in Radio Telecommunications Engineering at the same University. He is currently as a post-doctoral researcher with the Centre for Wireless Communications in University of Oulu, and Senior Member of the Institute of Electrical and Electronics Engineers. His current research interests are the design and analysis of wideband antennas, wideband multi-mode and full-duplex antennas, and antenna arrays, all including millimeter waves.
Mohamed Nabil Srifi is currently a professor of electrical engineering at Ibn Tofail University, Morocco. His research interests include RF and microwave passive and active circuits, antennas design and Wireless Sensor, biomedical engineering, EM, Numerical Methods FDTD. He is the head of Electronics and Telecommunication Systems Research Unit, Ibn Tofail University. He is the president of Moroccan Institute for Sciences and Development, member of the IEEE Microwave Theory and Techniques Society, IEEE Antennas and Propagation Society, European Microwave Association EuMA, Moroccan Association of Electricity, Electronics and Computers Engineering, Moroccan Association for Advanced Materials. He holds two patents on antennas for ultra-wide band applications. Moreover, he is the Founder and the General Chair of The International Symposium on Advanced Electrical and Communication Technologies.
This paper is for SI-aect. Reviews processed and recommended for publication to the Editor-in-Chief by Guest Editor Dr. M. N. Srifi.