Dependence of RFID Reader Antenna Design on Read Out Distance

Abstract

The design of a reader antenna is described for usage in Radio Frequency IDentification (RFID) systems at 13.56 Mhz, as defined in the ISO-14443a standard. It presents the theory, with emphasis on the effect of the read out distance on the design, but also describes measurements on concrete designs to validate the formulas and statements. We also comment on practical problems that were encountered during the design process. The major contribution of this work is the generalization of the design theory for large read out distances where the conventional assumption of constant loop current no longer holds. Index Terms-HF radio communication, loop antennas, magnetic fields, Q factor. 1 Activation range is defined as the distance from the reader where the field is still large enough to power up the tag. 2 Even if 10 cm is often suggested as the maximum range, the ISO-14443 standard does not mention this.

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 find a relationship between M a and M b thanks to equations (4) and figure 2 results, by introducing R 1a = x R 1b and centering at (0, 0, 0) the loops in figure 1, case 3. This drives to equations (6), (7) and (8).…”

Interrogation zone determination in HF RFID systems with multiplexed antennas

“…The antenna loop is typically made as a square [8], a rectangle [9], a circle [10] or other polygon [11]. The primary way to enlarge the size of IZ consists in conveying more energy to transponders that are freely deployed and oriented in the space Ω ID .…”

“…However, it is not possible to identify all transponders at any point in the space Ω ID . The most of all these problems are due to the fact that energy can be transferred from the RWD to transponders only on a limited distance [1,[7][8][9][10][11][12][13][14][15][16][17]. Additionally, many parameters and phenomena describing RFID systems have to be considered in a different way than it is in the classical theory valid for typical radio-communication systems.…”

3D RFID Simulation and Design - Factory Automation

“…If the loop becomes too large, however, these contributions become very weak due to the large distance from the current carrying part to the tag. Furthermore, if the total wire length of the loop becomes a considerable part of the wavelength of 22.12m , the standing waves will cause multiple resonances and decreases the total field [3,11]. Hence, the antenna dimension is determined experimentally to provide the sufficient magnetic field.…”