Dielectric Materials for Compact Dielectric Resonator Antenna Applications

Introduction Dielectric resonators using high-permittivity materials were originally developed for microwave circuits, such as filters or oscillators as tuning element [1]. Indeed, in the late nineteen sixties, the development of low-loss ceramic materials opened the way for their use as high-Q elements [2-4]. Then, making use of dielectric materials to create the dielectric resonator antenna (DRA) illustrates the ingenuity of Professor S. A. Long [5], who was the first to propose such a procedure in the early nineteen eighties. Indeed, it introduced the use of a dielectric resonator as an antenna by exciting different modes using multiple feeding mechanisms. During the nineties, emphasis was placed on applying analytical or numerical techniques for determining input impedance, fields inside the resonator and Q-factor [6]. Kishk, Junker, Glisson, Luk, Leung, Mongia, Bhartia, Petosa and so on, have described a significant amount of DRAs' analyses and characterizations [7-18]. Petosa and al. proposed both in literatures and book [6,12] many of the recent advances on DRAs. Current DRA literatures focus on compact designs to address portable wireless applications. Among them, new DRA shapes or hybrid antennas are developed to enhance the antenna impedance bandwidth [13-19] or for multiband antenna applications [20-22]. The first part will address a brief overview of the most common used DRA shapes and structures including both rectangular and cylindrical DRAs. The emphasis will be placed on better understanding what DRAs exactly are and how to develop such an antenna. This part will detail fundamental modes of DRAs, their resonant frequencies, fields inside the resonator and radiation patterns corresponding to these modes. A second part will focus on the relevant dielectric material properties having a significant contribution to achieve better antenna performances. It will detail the kind of materials DRAs can use, which is closely linked to the targeted application. Multiple techniques to miniaturize such an antenna will be presented in the third part, supported by concrete examples. At the same time, everyone will be able to appreciate that dielectric material properties have a major role to play in designing a DRA. It should be noted that the material choice is even more critical when the targeted challenge is the antenna size reduction. Therefore, depending on the intended applications, this part will enable to find the best trade-off between the material choice and its shape. Although some wideband or multiband DRA structures have been introduced in the third part, the fourth and last part will be dedicated to a new method to design a DRA. It will address engineering design data on hybrid modes creation to enhance the bandwidth or develop multiband antennas. This part will include many references to clearly explain this research method while highlighting their contribution to expand the use of DRA in new kind of mobile handheld devices (e.g. new tablets)

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Généralement, la borne de Cramer-Rao des directions d'arrivée de signaux sur un réseau de capteurs est calculée de façon théorique [1] [2] [3]. Or dès que l'on désire effectuer une application numérique de la borne de Cramer-Rao pour un système donné, on est souvent amené à effectuer des suppositions et/ou des simplifications. En effet, il est souvent très difficile de tenir compte et de modéliser l'environnement et les différents phénomènes pouvant perturber le réseau de capteurs, comme le couplage entre antennes, l'influence d'un porteur (mat ou véhicule) en termes de diffraction, de réflexion ou même la présence d'un sol. Dans ce travail, nous utilisons un logiciel de simulation électromagnétique pour estimer l'impact de l'environnement réel sur le vecteur direction d'un système antennaire complexe de goniométrie. La borne de Cramer-Rao déterministe des directions d'arrivée de signaux est ensuite déterminée pour le réseau de capteurs de goniométrie soumis à des perturbations. Les résultats montrent que la précision dépend fortement de la prise en compte des couplages et perturbations du système antennaire. On montre ainsi que l'environnement a un impact non négligeable et que l'on peut calculer une borne de Cramer Rao des directions d'arrivée plus réaliste et ainsi optimiser dans certains cas le système antennaire de goniométrie en fonction de son environnement

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This article presents the recent developments on electromagnetic band gap (EBG) resonator antennas. After reminding the working principles of such radiating devices, a state of the art is presented to show main applications of these antennas including high directivity solutions, multiband devices, omnidirectionnal coverages, focal feeds for reflector and tuning. Finally, some prospects are given for future improvements

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X-band compact dual circularly polarized isoflux antenna for nanosatellite applications

International audience— This paper presents an original solution to design a compact dual circularly polarized isoflux antenna (DCPIA) for nanosatellite applications. This kind of antenna has been previously designed in our laboratory, for a single circular polarization. This antenna is composed of a dual circularly polarized feed and a choke horn antenna. This feed is a cross-shaped slot in the ground plane which provides coupling between a patch and a ring microstrip line with two ports. It is located at the centre of a choke horn antenna. The simulated antenna presents an axial ratio (AR) lower than 3 dB and a realized gain (RG) close to 0 dB over a 400 MHz bandwidth (8.0-8.4GHz) at the limit of coverage (LOC), i.e. 65° whatever the azimuth angle (φ) and the port. A 20 dB matching for each port and 13 dB isolation characteristics between the two ports have been achieved on this bandwidth. It has been realized and successfully measured

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