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

Abstract

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.

Antenna array in 3D to improve tracking of small HF RFID tag

“…These resonators will modify the B-field distribution in function of their size, position, and tuning. This paper focuses on the potential of this second proposition, while the previous work [13] did not propose it. Another important difference with this previous work is that the size of the transponder, which was an ISO credit card size, can potentially be reduced because of the introduction of a resonator which will create some concentration of the B-field (increase in magnitude), and consequently the equivalent surface of the tag would be able to recover more power if its orientation is appropriate.…”

“…Previous studies [12][13][14] enable to propose some 3D structures for detection of the tags whatever their orientation and position, dynamically. Moreover, such structures suffer from the fast decrease of the B-field magnitude from the coils towards the centre of the structure, i.e.…”

“…in the case of a tube which will be presented in this paper, from the surface of the cylindrical exterior towards the central axis. Additionally, the distribution of the field, in the case of ICL [8,13,14], leads to a null field at the centre of the detection volume, due to the opposite phases of the currents and the symmetry of the structure. This is also the case for our study, as the ICLs structure is transposed in the case of the cube, as shown in Fig.…”

“…A theoretical approximation is made with a cube simulation and a practical detection test is performed thanks to a tube on which the sub-coils are conformed. In previous work [13], a tag card was used in simulation and measurements. The main goal of this part is to ensure detection in all angular orientations of the tag.…”

“…Therefore, the design maximises the range detection. These results have been partially presented in [13] and the novelty here is to combine the sub-coils structure in 2D and to add resonators in each of the sub-coils.…”