Publikace

In this article, we investigate a novel iterative antenna array synthesis method. The method is based on the iterative addition of antenna array elements. After defining the synthesis algorithm, we prove that the discrepancy between the goal and the synthesized pattern converges to the theoretical lower bound in the sense of a certain norm. The algorithm is also extended to iteratively replace already placed elements and for the synthesis of multiple goal patterns with the same array geometry but with different excitations. Some numerical examples are shown to illustrate the convergence properties of the proposed method. Possible applications include circularly polarized patterns, since the algorithm can handle the rotation as well as translation of the antenna elements.

In this paper, we propose a novel frequency domain reading method for the chipless RFID tags. It is based on a single scalar measurement of transmission coefficient magnitude between two antennas by the presence of a tag. The method enables to reliably read the chipless RFID tags based on a dipole resonator array, which is backed by a limited ground plane, in a real environment outside the anechoic chamber. Moreover, it suits simple, yet not necessarily well impedance matched, reader antennas represented by an open end of the rectangular waveguide. The method was verified experimentally in the frequency band of 7–11 GHz.

In this paper, we first carry out an in-depth review of the performance parameters of frequency domain chipless RFID transponders in terms of their spatial density, spectral capacity, and comprehensive encoding capacity (bit/lambda2/GHz) comprising both spatial and spectral performance, and platform tolerance. Secondly, we theoretically and numerically investigate the recently introduced and promising concept of the platform-tolerant chipless RFID transponder based on a detuned dipole array-plate that provides high encoding capacity. We propose, fabricate and measure a 20-bit transponder consisting of an array of 20 detuned dipoles closely coupled to a 60 × 60 mm2 metallic plate. The radar cross section at the level of 15 dBsm exhibits reliably recognizable minima corresponding to individual dipole resonances. When compared to other published frequency-domain chipless RFID transponders, the encoding capacity reaches 47.4 bit/lambda2/GHz, which constitutes one of the highest values, while achieving a concurrently high level of radar cross section (RCS) reflection response and platform tolerance performance. The measurements confirm very good performance parameters in the cases when the transponder is attached to various packaging materials, such as cardboard, plastic, wood, metal or a human body phantom. The essential benefits of the presented solution include a very good frequency and amplitude stability in the RCS response, which enables a reliable reading of encoded information (if zero bits are coded). The double layer metallization represents an inherent property of the proposed solution, which is a necessary trade-off for high encoding capacity and contemporary platform tolerance.

A novel planar chipless radio frequency identification (RFID) tag is introduced in this paper. The tag is composed of miniaturized multiple reflecting antennas based on a slow wave structure. To validate the proposed approach, a tag with a coding capacity of 16 bits has been designed with a compact size of 15 × 21 mm². Tags with different pattern configurations have been performed using a Rogers RO4003 substrate and its radar cross-section responses have been measured. Compared to conventional multi-resonator tags, the proposed tag offers a good miniaturization ratio and spectral coding efficiency. In addition, the measurements revealed high Q factor and coding robustness which demonstrates the efficiency of the used approach to develop high performance chipless tags.

The analysis of capacitive wireless power transfer was conducted in a general manner. The circuit model of a capacitive wireless power transfer chain was presented. The derivation of the power transfer efficiency through the chain in question as well as the active power delivered to the appliance terminating this chain was shown. Both the case of the maximal efficiency and the one of the maximal appliance power were treated and conditions for these optima were found in both cases. The appliance power corresponding to the maximal efficiency and the efficiency corresponding to the maximal appliance power were also expressed. The total admittance of the capacitive wireless power transfer chain was calculated. For both optimal conditions, the appliance power and total admittance were written in the normalized form, which enabled to express them as functions of single variable in the same way as the efficiency.

The paper presents the novel 20-bit chipless RFID transponder (tag) based on spiral capacitively loaded dipole scatterers of electrical size ka = 0.47, radar cross section σ = 29.3 dBsm, and bandwidth BW3dB = 20.9 MHz. It outperforms U-folded dipole scatterer (ka = 0.79, σ = 34.3 dBsm, BW3dB = 18.1 MHz) in the first two parameters in exchange for a slight increase in bandwidth. The total tag size (17 × 68 mm2) is roughly half the size of a credit card. The frequency and amplitude stability of its RCS response, when the zero bit information is coded via removal of individual scatterers, is improved by reordering scatterers in the array. The simulated results were verified by the monostatic measurement of tag RCS.

This article presents recent European-based contributions for wireless power transmission (WPT), related to applications ranging from future Internet of Things (IoT) and fifth-generation (5G) systems to highpower electric vehicle charging. The contributors are all members of a European consortium on WPT, COST Action IC1301 (Table 1). WPT is the driving technology that will enable the next stage in the current consumer electronics revolution, including batteryless sensors, passive RF identification (RFID), passive wireless sensors, the IoT, and machine-to-machine solutions.

This paper describes properties of a new 20-bit chipless RFID tag of the size 52 × 50 mm2, which exhibits an improved magnitude and robustness of the radar cross section (RCS). The tag is based on a novel slots-in-plate array approach, which is complementary to a typical tag consisting of an array of single resonators. In order to eliminate the detuning effect of the missing or shortening slots representing ‘0’ bit information on the resonances of neighbouring slots signifying ‘1’ bit information, the modification of the inter-element arrangement was proposed. Both ways of ‘0’ bit information coding were studied and compared.

We propose a novel chipless RFID tag composed of topologically modified uniplanar U-folded dipoles with inclined arms. This topology reduces the interelement mutual coupling and provides a significantly better amplitude uniformity and frequency stability of tag RCS response when logical “0” is coded by removing particular scatterers from the array. Simultaneously, it provides a higher encoding capacity in unit frequency range than the arrays composed of original U-folded dipoles with parallel arms, yet at the expense of small RCS magnitude reduction.

This review paper presents the summary of our investigations in several topics of frequency-domain chipless RFID transponders. The performance comparison of various types of scatterers used in the literature and recently proposed by the authors is presented. The issue of proper location of adjacent resonant elements in the scatterer array to reduce the mutual coupling and consequently ensure the robust RCS response for reliable reading of coded information is addressed. A major improvement in RCS response of transponders is proposed, using slot-in-plate type transponders. Advantages and drawbacks of the proposed solutions are discussed and several open challenges in the field are emphasized.