Effect of added resonators in RFID system at 13.56 MHz

Abstract

In this study, a reader antenna including resonators is proposed to improve detection of a small moving tag in the case of tracking a radiofrequency identification (RFID) system. The near-field RFID technology is based on load modulation, the input impedance on the reader coil and the mutual inductance between the reader and tag coils are the main parameters for performing detection. They are calculated from the impedance matrix parameters. The added resonators change all the parameters of the impedance matrix consequently the input impedance and mutual inductance are also changed. In this study, analytical formulation defining the equivalent impedance matrix parameters is developed. These formulae are used to evaluate the performance of the proposed design according to the tag misalignment (lateral and angular). From the calculation and simulation results, a frequency shift in the equivalent input impedance is found. To avoid this problem, optimising the positioning of the resonators on the reader coil is performed. This study is confirmed by measures of RFID detection for a reader prototype (with and without resonators) and a small commercial tag. Both the surface and volume of detection of the small moving tag (lateral and angular misalignment) are improved by the principle of added resonators.

Low-cost thin-film passive RFID circuits and detector system

“…From the power point of view, the RFID systems are sub-categorized into active [2], semi-active [3, 4], and passive [5–7]. Moreover, from the communication range point of view, they are sub-categorized into three main categories: close coupled [7, 8], remote coupled, and long range [9, 10]. Nowadays, several applications facilitate the use of simple passive RFID tags to limit the cost of the ID tag unit and introduce relatively more complexity to the reader design.…”

“…On the other hand, applications with lower frequencies in the order of 10 MHz are used more for relatively very short-range applications. Hence, ID tag design depends very much on lumped element planar patterns such as spiral inductance and interdigitated capacitances [8]. Most current RFID systems involve a silicon chip that would set a limit on the total achievable system cost.…”

Design, optimization and realization of high gain RFID array antenna 4 × 1 for detection system of objects in motion

“…Due to cost effectiveness and mass production, most of the tags are passive only (figure 1). Currently, much effort has been devoted to the development of RFID techniques, since RFID systems have found a wide range of applications in many fields [3][4][5][6][7][8]. Indeed, an antenna is an important part of these RFID systems, since it allows tag and reader to communicate and exchange data.…”