Low-power dual-band on-body antenna for wireless body sensor networks

In Wireless Body Area Network (WBAN), the implanted biosensor collects various physiological data and wirelessly transmits the information to external medical devices in real time. The antenna design for this application faces great challenges as the microwavepropagation medium is not the free space as the human tissues constitute part of the transmission channel. The effects of the human body should be taken into consideration during the antennadesign.The present thesis aims to arrive at the optimum design of the on-body antenna to operate as a central antenna for WBAN. Five types of helical antennas are proposed in the present thesishaving a dual-frequency operation at 2.45 GHz and 5.8 GHz. The proposed antennas are optimized to maximize the Signal-to-Noise-Ratio (SNR) and, hence, to minimize the BER and the Specific Absorption Rate (SAR) in the human tissues. In this thesis, a semi-analytic rigorous technique for the assessment of microwave propagation on the medium equivalent to the human body is developed and the radiated fields from the proposed on-body antennas in the near zone are evaluated.The commercially available CST® simulator is used and experimental measurements are done for the five fabricated prototypes. The near-field distribution over the surface of humanbody is evaluated at 2.45 GHz using a Matlab® program, while the far-field radiation patterns obtained by experimental measurements showing good agreement with those obtained by the CST® simulator. It is shown that the radiation patterns produced by the more compact antennas; the conical-helix monopole and the monopole-spiral antennas show better performance and moreappropriate for the intended application.It is clear from the obtained results that the conical-helix/monopole and the monopole-spiral antennas have the highest performance. These antennas are shown to achieve the minimum BERof 5.3 × 10-5 and 6× 10-8 for both antennas respectively. In addition, the minimum average of the SAR that does not exceed 0.3 W/Kg in the human tissues while consuming the minimum valueof the input power when compared with the other antenna types

Antenne hélice compacte directive à polarisation circulaire pour dispositif RFID

Over the past 20 years, the RFID (Radio Frequency Identification) technology is having a huge expansion. Nowadays, it is frequently used in different areas as the health, the security and the logistic. A lot of researches are ongoing on this topic, especially in order to reduce the reading zone of the readers and to locate the tags. This thesis focuses on the development of new antennas for Readers RFID devices and is part of the SPINNAKER project supported by OSEO. The antennas requirements are circular polarization, high directivity and gain with low profile. The helix antennas meet all these requirements except the axial length. In this manuscript, we propose three solutions to reduce the helix antenna axial length. The first one uses a cylindrical or conical optimal reflector to reduce the length by four. This reduction affects directly the surface witch increases up to 2.3λ. The second solution uses the helix antenna as a circular polarization feed for a Fabry-Perot (FP) cavity. The final antenna presents a cavity height of 0.5λ and a 2λ diameter. The last solution conserves the FP cavity in which we include an Artificial Magnetic Conductor (AMC) to reduce the cavity height to 0.25λ. All these solutions are validated by measurements.La technologie RFID (Radio Frequency Identification) prend une place de plus en plus importante dans la société d'aujourd'hui notamment dans des domaines aussi variés que la santé, la sécurité, la logistique... Le développement de cette technologie met en évidence de nouvelles contraintes comme la réduction des zones de lecture et la géo-localisation pour le stockage et le suivi de marchandises. Dans ce contexte, la thèse s'est focalisée sur le développement d'antennes pour lecteur RFID dans le cadre du projet SPINNAKER piloté par TAGSYS RFID et soutenu par OSEO. L'objectif de cette étude est de concevoir des antennes compactes et directives à polarisation circulaire en bande UHF et SHF. L'antenne hélice présente toutes ces caractéristiques à l'exception de la hauteur, très importante dès que l'on souhaite obtenir des performances élevées surtout en gain. Dans ce manuscrit, trois solutions sont proposées pour réduire la hauteur de l'antenne hélice tout en répondant aux cahiers des charges. La première solution consiste à utiliser un réflecteur de forme cylindrique ou conique qui permet de réduire la hauteur d'une antenne hélice classique d'un facteur quatre pour atteindre 0,9λ. La réduction de la hauteur se traduit par une augmentation de la surface autour de l'antenne avec une dimension latérale de 2,3λ. La seconde solution consiste à utiliser l'antenne hélice avec une cavité Fabry-pérot. La hauteur du système antennaire obtenue est de 0,5λ avec un diamètre de 2λ. La dernière solution développée dans la thèse introduit une surface CMA à la solution précédente qui permet de réduire la hauteur à 0,25λ. Toutes les solutions proposées ont été validées expérimentalement

Неуниформне хеликоидалне антене

The objective of this thesis is to systematically analyze and optimize nonuniformly-wound helical antennas, along with classical (uniform) helical antennas. The optimization of the nonuniform helical antennas has many degrees of freedom. Hence, the optimization space is large and the optimization task is challenging. It is shown that, in most practical cases, the optimal nonuniform helical antennas outperform the uniform helical antennas presented in the literature. It is also shown that the nonuniform helical antennas are the preferable choice when the losses are low or medium, whereas for high losses, the uniform helical antennas should be used. A large database is assembled from the optimization results, wherefrom a complete design procedure is developed for the nonuniform helical antennas. This procedure comprises all necessary equations and graphs for evaluating the optimal antenna parameters and estimating the antenna characteristics. The design procedure is verified experimentally, by measurements of a fabricated prototype. Quad (2 x 2) arrays of nonuniform helical antennas are also investigated. Their design procedure includes the optimization of single antennas along with their positions in the array. The solution of a real engineering problem is presented: a quad array that meets predefined specifications is designed and a prototype is fabricated and measured.Циљ ове тезе је систематична анализа и оптимизација неуниформно мотаних хеликоидалних антена, као и класичних (униформних) хеликоидалних антена. Оптимизација неуниформних хеликоидалних антена има много степени слободе. Стога је оптимизациони простор велики, а оптимизација изазован задатак. Показано је да, у највећем броју практичних случајева, оптималне неуниформне хеликоидалне антене надмашују по перформансама униформне хеликоидалне антене представљене у литератури. Осим тога, показано је да су неуниформне хеликоидалне антене бољи избор када су губици мали или средњи, док би у случају великих губитака требало користити униформне хеликоидалне антене. Резултати оптимизације чине велику базу података, на основу које је развијен поступак пројектовања неуниформних хеликоидалних антена. Овај поступак обухвата све потребне једначине и графике за одређивање оптималних параметара антена и процену карактеристика антена. Поступак дизајна је потврђен експериментално, мерењем карактеристика реализованог прототипа. Такође су испитивани низови од 2 x 2 неуниформне хеликоидалне антене. Процедура за њихов дизајн садржи оптимизацију засебних антена, као и оптимизацију положаја антена у низу. Представљено је и решење реалног инжењерског проблема: дизајниран је низ од 2 x 2 антене који испуњава унапред дефинисане спецификације, а прототип је направљен и измерен

Wideband and UWB antennas for wireless applications. A comprehensive review

A comprehensive review concerning the geometry, the manufacturing technologies, the materials, and the numerical techniques, adopted for the analysis and design of wideband and ultrawideband (UWB) antennas for wireless applications, is presented. Planar, printed, dielectric, and wearable antennas, achievable on laminate (rigid and flexible), and textile dielectric substrates are taken into account. The performances of small, low-profile, and dielectric resonator antennas are illustrated paying particular attention to the application areas concerning portable devices (mobile phones, tablets, glasses, laptops, wearable computers, etc.) and radio base stations. This information provides a guidance to the selection of the different antenna geometries in terms of bandwidth, gain, field polarization, time-domain response, dimensions, and materials useful for their realization and integration in modern communication systems

Beam scanning by liquid-crystal biasing in a modified SIW structure

A fixed-frequency beam-scanning 1D antenna based on Liquid Crystals (LCs) is designed for application in 2D scanning with lateral alignment. The 2D array environment imposes full decoupling of adjacent 1D antennas, which often conflicts with the LC requirement of DC biasing: the proposed design accommodates both. The LC medium is placed inside a Substrate Integrated Waveguide (SIW) modified to work as a Groove Gap Waveguide, with radiating slots etched on the upper broad wall, that radiates as a Leaky-Wave Antenna (LWA). This allows effective application of the DC bias voltage needed for tuning the LCs. At the same time, the RF field remains laterally confined, enabling the possibility to lay several antennas in parallel and achieve 2D beam scanning. The design is validated by simulation employing the actual properties of a commercial LC medium

Design and Analysis of a Cylindrical Dielectric Resonator Antenna Array and Its Feed Network

There is an ever increasing need for smaller, lighter, more efficient antennas for commercial and military applications. One such antenna that meets these requirements is the dielectric resonator antenna (DRA). In recent years there has been an abundance of research on the utilization of the DRA as a radiating element. However, its practical application - especially pertaining to DRA arrays - is still considered to be at its infancy. The purpose of this work is to present a systematic process to be used in the design, simulation, optimization, fabrication, and testing of a cylindrical DRA array including its associated feed network. The DRA array development cycle begins with a single cylindrical radiating element. ComDRA parameters such as DRA radius, feed type, feed location, and element spacing are investigated. A DRA element in this research is optimized for bandwidth and gain for use at x-band (8-12 GHz). The antenna feed network, being an integral part of all antenna arrays, is also considered. The primary causes of impedance mismatch in the feed network are identified and techniques to improve performance are explored. An improvement in impedance bandwidth is gained through traditional transmission line matching methods. Ultimately, a 16 (4x4) element and 256 (16x16) element array is fabricated, tested, and compared to an existing commercial technology