Design and Measurements of a Quasi-isotropic UWB Planar Antenna

ISSN 1874-4761This paper summarizes the design and measurements of a quasi-isotropic printed UWB antenna, with the analysis of its performances through defined figures of merit. State of the art and review of some recent patents give us the opportunity to exploit some empirical considerations about the shape and the methodology of conception. A simple structure is simulated by means of CST Microwave Studio to show the possibility of fulfilling, at a defined level, UWB antenna requirements such as matching, fidelity and quasi-isotropy of the radiation pattern with a simple micro-strip design and a standard technology. The design of this antenna is based on considerations about bulbous and bended traveling wave antennas. Results of its characterization in anechoic chamber are quantified in terms of amplitude and phase variation, in order to illustrate the level of dispersion for the different directions. The article presents some promising patents on quasi-isotropic UWB antenna

Radio-Communications Architectures

Wireless communications, i.e. radio-communications, are widely used for our different daily needs. Examples are numerous and standard names like BLUETOOTH, WiFI, WiMAX, UMTS, GSM and, more recently, LTE are well-known [Baudoin et al. 2007]. General applications in the RFID or UWB contexts are the subject of many papers. This chapter presents radio-frequency (RF) communication systems architecture for mobile, wireless local area networks (WLAN) and connectivity terminals. An important aspect of today's applications is the data rate increase, especially in connectivity standards like WiFI and WiMAX, because the user demands high Quality of Service (QoS). To increase the data rate we tend to use wideband or multi-standard architecture. The concept of software radio includes a self-reconfigurable radio link and is described here on its RF aspects. The term multi-radio is preferred. This chapter focuses on the transmitter, yet some considerations about the receiver are given. An important aspect of the architecture is that a transceiver is built with respect to the radio-communications signals. We classify them in section 2 by differentiating Continuous Wave (CW) and Impulse Radio (IR) systems. Section 3 is the technical background one has to consider for actual applications. Section 4 summarizes state-of-the-art high data rate architectures and the latest research in multi-radio systems. In section 5, IR architectures for Ultra Wide Band (UWB) systems complete this overview; we will also underline the coexistence and compatibility challenges between CW and IR systems

A New Criterion to Jointly Design the Antenna and Optimize the Communication Capacity in IR-UWB.

International audienceThis paper presents the impact of the antenna design over the capacity of a IR-UWB system in a Multi-User Interference environment. A new antenna design is proposed and it is showed using a new performance criterion that for this design, the communication capacity given by the Sholtz's pulse [13] might be reached using some other types of pulses

Analyse de l'influence du codage d'enveloppe sur les performances de l'amplificateur classe E d'une architecture polaire.

National audienceAujourd'hui on observe une augmentation de la dynamique des signaux pour les nouveaux standards. L'utilisation d'amplificateurs linéaires ne permet pas d'obtenir de forts rendements. On peut envisager d'utiliser des amplificateurs en classe commutée associés à une architecture polaire fournissant un signal à enveloppe constante. Cela grâce à un codage de l'enveloppe par un modulateur de type ΣΔ . Le but de cet article est de comprendre l'influence que peut avoir la forme d'un signal binaire sur les performances en commutation d'un amplificateur classe E conçu pour une application Wimax mobile (3.7GHz). L'article étudie les performances pour différentes répartitions probabilistes des niveaux à plusieurs fréquences de codage

Equivalent input and output impedances in HF RFID system including resonator

High Frequency Radio Frequency Identification (HF RFID) system based on Magnetically Coupled Reader Resonator Coils (MCRRC) is reported. The proposed system consists of reader antenna including small resonant coil operating by magnetic coupling with the tag coil. In the proposed system, the reader and tag impedances are modified. The equivalent electrical model is used to express the equivalent impedance matrix and used to express the equivalent input and output impedances of the system. The formulas are confirmed by comparison between High Frequency Structure Simulator (HFSS) results and measures

Improvement of HF RFID detection for small and misaligned tag

A design of a reader antenna is proposed to optimize HF RFID range detection in parallel and perpendicular configuration. The reader antenna has a surface of 500 cm2, the tag corresponds to 0.7% of the reader surface. For passive RFID system, if the reader antenna does not provide the threshold energy to the tag, this one will not be detected. This is the case of the misalignment systems with great difference size antenna. Another problem limiting RFID detection is the different possible tag orientations. In perpendicular configuration, the detection is weak, the tag can only be detected above the edges of the antenna. These limits are minimized in this work by using a multiple loop antenna including resonators. Electrical model is developed to calculate the equivalent mutual inductance of the system from the impedance matrix: the measured results confirm the simulated ones. The detection measurements validate the improvement

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

This paper presents an improvement of small RFID tags detection in HF near field, whatever their lateral and angular misalignments, using a complementary sub-coils reader antenna, enhanced by coplanar weakly-coupled resonators, and conformed on a 3D tube. The key ideas of detection improvement are: (i) modification of B -field vector distribution with the complementary coils above the common edge of consecutive loops; (ii) increase of B -field vector diversity and magnitude distribution by a 3D structure conformed on the tube, by realising 2 pairs of Identical Coaxial Loops (ICLs) with face-to-face sub-coils in forward current, and (iii) enhancement of B -field magnitude distribution by resonators included in the complementary sub-coils. Numerical simulations are carried out using High Frequency Structure Simulator (HFSS). The studied figure-of-merit is the mutual inductance between the tag and the reader coil. Results are reported for the 4 planar complementary sub-coils, the previous structure conformed on the tube and for the structure in which RCL resonators are added in the 3 planar complementary sub-coils. Experimental detection range measurements of each fabricated structure drives to the enhancement of the 3D complementary 4 × 3 sub-coils structure with weakly-coupled RLC resonators in each-sub-coil in terms of read-out distance and detection surface area

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

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

Array sub-loops reader antenna for HF RFID tracking

This paper focuses on tracking and objects identification by means of High Frequency magnetic coupling RFID (Radio Frequency IDentification) at 13, 56 MHz. The coil of the used RFID tags corresponds to 1.9% of the reader coil surface (120×160 cm 2 ). To increase the size ratio between the two coils, we proposed the use of multiple twisted loops antenna. The reader antenna is consequently divided into four sub-loops, corresponding to 8% of the surface of each one of the sub-loops area. According to the principle of twisted loop antenna, the nearest sub-loops are feed by current in opposite phase (complementary loops principle), and. This structure creates a strength curvature of magnetic field lines between each two of them, improving the magnetic coupling for vertical magnetic dipoles. In contrast, the structure presents at its center a null of magnetic field intensity due to the symmetry. To avoid this inconvenient a resonator is added to the structure to broke the symmetry and modify the magnetic field distribution. Its positioning is studied to optimize RFID detection in different angular and lateral positioning of the tag. Simulations and measurements of the proposed design with and without resonator are presented in the different parts of this paper

Effect of added resonators in RFID system at 13.56 MHz

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