Megdouda Benamara

Improvement of HF RFID Tag Detection With a Distributed Diameter Reader Coil

This letter focuses on 13.56 MHz high-frequency radio frequency identification (RFID) in the case of small tags detection, with an effective area below 1 cm2. In such an identification system, based on load modulation principle, the magnetic coupling coefficient k and quality factor of the RFID reader coil are the key parameters. The main goal of this letter is to improve the detection of small tags over a given surface of 10 × 10 cm2 by modifying the reader coil structure, and consequently the coupling coefficient k. Several coil designs are compared experimentally by distributing the diameters of their turns among three possible values. The design of the coils is based on empirical formulas that are in good agreement with experimental measurements. Electromagnetic simulations are performed to confirm the magnetic field distribution of the different designs. The results show that distributed diameter coil (DDC) as RFID reader coil is clearly efficient in this context of the RFID detection. The DDC structures determine the k factor, and, as k is low, the quality factor Q is a second parameter that can improve, in a second step, the RFID detection performances in function of the tag position and orientation.

3D HF RFID reader antenna for tag detection in different angular orientations

Herein, a 3D 13, 56 MHz (HF) RFID reader antenna is proposed in order to optimize detection performance whatever the tag angular positioning. The design is made of a multi-loop structure, based on serial complementary antennas, as said “twisted” antennas. The RFID tag detection is optimized by two factors which rely on the modifications of the magnetic field (i) vectorial distribution and (ii) magnitude density. The reader antenna design is analyzed with electromagnetic simulation under HFSS (High Frequency Electromagnetic Field Simulation), and validated by detection measurements, in coplanar mode. A multi-loop structure, composed by 4 sub-loops, is then conformed onto a tube surface to provide the 3D structure. The goal of this improvement is to provide tag detection for any angular positions. At the center of the tube (3D reader structure), the detection of the tag is performed whatever its angular orientation, that is to say for any radial orientation.

Sub-coil in reader antenna for HF RFID volume detection improvment

This paper proposes a reader antenna, improving the inductive coupling with a small coil whatever its position or orientation against the reader antenna. Sub-coils are inserted and the turn number is optimized in order to improve efficiency of the inductive coupling in the case of HF RFID volume detection in keeping constant the magnetic energy generated by the reader.

Array sub-loops reader antenna for HF RFID tracking

This paper focuses on tracking and objects identification by means of High Frequency magnetic coupling RFID (Radio Frequency IDentification) at 13, 56 MHz. The coil of the used RFID tags corresponds to 1.9% of the reader coil surface (120×160 cm2). To increase the size ratio between the two coils, we proposed the use of multiple twisted loops antenna. The reader antenna is consequently divided into four sub-loops, corresponding to 8% of the surface of each one of the sub-loops area. According to the principle of twisted loop antenna, the nearest sub-loops are feed by current in opposite phase (complementary loops principle), and. This structure creates a strength curvature of magnetic field lines between each two of them, improving the magnetic coupling for vertical magnetic dipoles. In contrast, the structure presents at its center a null of magnetic field intensity due to the symmetry. To avoid this inconvenient a resonator is added to the structure to broke the symmetry and modify the magnetic field distribution. Its positioning is studied to optimize RFID detection in different angular and lateral positioning of the tag. Simulations and measurements of the proposed design with and without resonator are presented in the different parts of this paper.

Design of 1cm 2 coils for HF RFID instruments tracking with detection range improvement

This paper concerns an application of magnetic coupling RFID technology at 13.56 MHz (HF band) for tracking devices such as instruments. The tag size is defined to be ergonomically small compared to the hand, and fixed inside a maximum surface of 1 cm2. The case of multiple detections is considered, and consequently the reader surface of control is considered wide enough to include several instruments at the same time during a logistic control process. The use of such a small RFID tag is almost impossible using a large reader loop of 15×30 cm2, as chosen for the tests. The key idea of the paper is then the addition of a resonator that enables to create the mandatory physical link by means of magnetic coupling between the tag coil and the resonator coil and between the resonator coil and the reader loop. Finally the detection range is highly improved by the presence of this resonator and results demonstrate that it is possible to detect these small RFID “1 by 1 cm2 tags” at a distance of 1.5 cm to 3 cm, depending on their orientations.

Distributed Diameter sub-Coil Twisted Loop Antenna in non-radiative WPT

This letter focuses on the high-frequency wireless power transfer by electromagnetic induction and its dependence on the lateral misalignment and tilt of the small receiving coil relative to the transmitting coil. We combine two structures, the twisted loop antenna (TLA) and subcoils of a distributed diameter coil (DDC) for transmitting designs. Our system is then referred to as TLA-DDC. The radius of the subcoils is parametrically varied for different distances between the coils and performed in two positions for each distance (coaxial position when the receiving coil is parallel to the plane of the transmitting coil, and center position for the perpendicular orientation of both coils). Then, using different radii for the transmitting DDC TLA when the receiving coil is moved onto its surface allows us to obtain a greater value of efficiency at different positions: up to 2.4 times for the peak value and 1.5 for the average value for receiving coil in parallel plane. The efficiency of the magnetic coupling is determined by means of power efficiency with a comparison between the DDC TLA antennas and a standard coil antenna corresponding to the same inductance value.

Reader antenna including resonators for HF RFID detection

In this article, HF RFID reader antenna including small resonant coil, operating with the magnetic coupling with the reader coil, is reported. The proposed system is used to improve surface and volume of small tag detection. The performances of such system are validated by maximization of input impedance (load modulation principle) and equivalent mutual inductance between the reader dual-coils and the tag coil compared to a conventional RFID reader antenna. Analytical formulas of theses parameters are developed. The proposed system is validated by detection measurements in parallel and perpendicular configurations between the reader and the tag coils.