Detecting range and coupling coefficient tradeoff with a multiple loops reader antenna for small size RFID LF tags

Abstract

International audienceThis paper summarizes some tests with Low Frequency (LF, 125 kHz) RFID tags of two types: Card and Token. These tests were done in order to evaluate the feasibility of an identification/traceability of tags which size is constrained and supposed to be detected inside a delimited volume of 40x40x10 cm3. As the size of the antenna tag is supposed to be very small, we improve the detection range and volume of definition by designing different reader antennas. Reader antennas presented are of two types whether they are based on single (SL) or multiple loops (ML). Detection range was evaluated for planar antennas (3 SL and one ML). Volume of definition for the detection was estimated by designing two-level prototypes of ML antennas. Results are discussed about the optimization possibility of detection range and volume thanks to M

Detection tube for small HF RFID tags, based on mutual coupling with a coil resonator

“…We investigated magnetic coupling solutions for that reason because HF and LF are less sensitive to the metal (magnetic coupling phenomenon) and are in a frequency band lower than communications systems (GPS, GSM, 3/4G, WiFi) and ISM (2.4/5GHz). Some low-cost LF prototypes were tested [5] [6] and the conclusion is that it is possible to use this technology but the penalty is the very high number of turns needed for realizing loops antennas for a sufficient reactance value. In this paper, we focused on the HF magnetic coupling solution and, for the prototypes, use the 13.56 MHz ICODE SLI-X long-range chips from NXP with a RFID reader from IB Technology.…”

“…If possible, multiple detections ability is preferred. Consequently, we investigated the principle of detection in volume, for the tagged mMDs, driving us to consider a case study of magnetic coupling where the sizes of the tag and reader loops are very different [5][6] [7]. Such problematic is presented in Figure 1 with additional consideration about tag orientations.…”

“…Also, the value of M is highly decreasing with the distance and can be the reason of a non RFID tag detection if the limit for powering the chip is below the possible values for M. To counter this decrease in the mutual coupling effect, the case 3 in Figure 1 expressed the geometrical consideration of multiple loops possibilities. As studied in the literature and in past works at LF [5] [12], the geometrical criterion is highly efficient for magnetic coupling increasing if the reader loop/coil structure is optimized and more complex. In HF, the principle of "magnetic-field-guide" is preferred due to the electrical imperfections added by the connections (parasitic capacitance especially).…”

Improving LF reader antenna volume of detection for RFID token tag thanks to Identical Coaxial Loops (ICLs) and in/out-of phase multiple-loops structures

“…We can summarize the detection performances by these observations: -Inside the volume of control, and in each volume determined by the ICL, a tag in parallel position is detected, as in [14]. If a tag in this position is moving inside the volume, it will be detected, except if its trajectory is exactly following the symmetry axis of the structure ("between" all the loops).…”

Pebbles Tracking Thanks to Rfid Lf Multi-Loops Inductively Coupled Reader

“…The loops can be associated in serial or parallel configuration in forward and reverse sense to modify the B-field distribution and assure better energy transfer efficiency between the loops. Multi-loops arrays, by splitting the loop in small loops, can improve the null-zone avoidance using the diversity combining of loop [3,4] or by including several forward and reverse loops can provide free TAG positioning [5,6] and orientation [7,8].…”