Conception d'Antennes Planaires Reconfigurables pour Opération Large Bande et Multi-Bande

The work presented in this thesis concerns the study and design of frequency reconfigurable antennas for wireless application systems. After introducing the printed antennas, including the characteristics of this type, feeding techniques, and the description of the fractal antennas, UWB antennas and multiband antennas. A state of the art on reconfigurable antennas and the different types of reconfiguration that exist were discussed. The first part of the practical implementation is focused on the fabrication of new three fractal antennas have to operate at the frequency band allocated by the Federal Communications Commission (FCC) for Ultra-Wideband (UWB) applications. The second part of this thesis, several prototypes of reconfigurable antennas allowing various functions (a switch between multiband mode) were simulated and realized. The approaches more original considered have been implemented with real switches (PIN diode). The experimental results agree with those obtained by simulation and validate a reconfigurable operation mode necessary for multimode communication systems.Le travail présenté dans cette thèse concerne l'étude et la conception d'antennes reconfigurables en fréquence pour les applications sans fil. Après avoir introduit les antennes imprimées, y compris les caractéristiques de ce type d’antennes, les techniques d’alimentation, ainsi qu’une description sur les antennes fractales, Ultra Large Bande (ULB) et multi-bandes. Un état de l’art sur les antennes reconfigurables et les différents types de reconfiguration existant ont été discutés. La première partittte est focalisée sur la réalisation pratique de trois nouvelles antennes fractales pour fonctionner dans la bande de fréquence allouée par la Commission fédérale de communication (FCC) pour les applications Ultra Large Bande (ULB). Dans la seconde partie de cette thèse, plusieurs prototypes d'antennes reconfigurables permettant diverses fonctions (un basculement entre mode multi-bandes) ont été simulés et réalisés. Les approches plus originales jugées, ont été implémentées avec des interrupteurs réels (diodes PIN). Les résultats expérimentaux concordent avec ceux obtenus par simulation et valident bien un fonctionnement reconfigurable nécessaire pour les systèmes de communication multimodes

Compact coplanar waveguide‐fed reconfigurable fractal antenna for switchable multiband systems

In this study, a coplanar waveguide-fed reconfigurable antenna using crescent-shaped fractal geometry is presented. The frequency reconfigurable approach is obtained using radio-frequency positive intrinsic negative diodes, resistor, and inductors. The proposed approach has successfully allowed reconfigurable switching up to eight frequency bands between 1.46 and 6.15 GHz. Good results have been obtained in terms of stable and omnidirectional radiation patterns. The realised gains of the antenna system, in these frequency bands, vary from 0.52 to 5.67 dBi. The designed antenna has the advantages of a multiband structure and compact size over the previously reported structures. The proposed antenna is suitable for future wireless application systems

A Wearable Circularly Polarized Antenna Backed by AMC Reflector for WBAN Communications

A new flexible circularly polarized (CP) wearable antenna is proposed for Wireless BodyArea Network systems (WBAN) operating at 5.8 GHz. The circular polarization is enabled by combining a microstrip-line monopole feed and an inverted L-shaped conformal metal strip extended from a coplanar waveguide. The proposed antenna shows satisfactory performance in terms of gain and specific absorption rate (SAR) at a separation of 12 mm from a human body model. To minimize body-antenna separation, a flexible 2 × 2 artificial magnetic conductor (AMC) was used as a reflector to achieve good performances in terms of gain and SAR. The total footprint of the proposed antenna is only 34.4 × 34.4 mm2(0.384 λ20) board of semi-flexible Rogers RT-Duroid 5880 substrate. The final design provides a peak gain of 7.6 dBi and an efficiency of 94.7% when worn on the body. Furthermore, evaluation results indicate that the maximum SAR level decreased by up to 20.42% in comparison with the CP antenna without the AMC. Full-wave EM simulation and experimental results are performed, both in free space and proximity to the human body under different bending scenarios. Overall, the proposed antenna performance has been shown to be robust to structural deformation along the x-axis in comparison to previously reported designs. These features demonstrate that the proposed antenna is a strong candidate for off-body wearable applications

A compact CPW-Fed hexagonal antenna with a new fractal shaped slot for UWB communications

International audienceIn the present paper, a simple and compact a coplanar waveguide (CPW)-Fed hexagonal antenna has been presented. The proposed antenna is composed of a new fractal shaped slot with a hexagonal patch fed. The total size of the presented antenna is 14.5×16.5 mm 2 , which is designed on Rogers RO4350B substrate and having dielectric constant ε r =3.66, a thickness of h=1.524 and loss tangent of 0.004. The impedance bandwidth, defined by -10 dB reflection coefficient. Hence, the simulated results get a proper agreement with an impedance bandwidth of 2.98 GHz to 11.4 GHz. The investigated antenna is suitable for UWB applications. The design validation of the fractal antenna has been achieved by using CST Microwave studio

Design of reconfigurable fractal antenna using pin diode switch for wireless applications

International audienceIn this article, a frequency reconfigurable fractal patch antenna using pin diodes is proposed and studied. The antenna structure has been designed on FR-4 low-cost substrate material of relative permittivity εr = 4.4, with a compact volume of 30×30×0.8 mm3. The bandwidth and resonance frequency of the antenna design will be increased when we exploit the fractal iteration on the patch antenna. This antenna covers some service bands such as: WiMAX, m-WiMAX, WLAN, C-band and X band applications. The simulation of the proposed antenna is carried out using CST microwave studio. The radiation pattern and S parameter are further presented and discussed