L'objectif de cette thèse est d'étudier la faisabilité et les performances d'un synthétiseur de fréquences agile pour les transmissions multi-bandes multi-utilisateurs destinées aux systèmes de transmission fournissant un très grand débit tout en répondant aux exigences de faible consommation et d'intégration facile. Dans ce contexte, les solutions classiques de synthétiseur de fréquences ne sont pas applicables et il est nécessaire de développer de nouvelles structures qui génèrent les fréquences centrales en permanence. La commutation d'une fréquence à l'autre peut se faire alors très rapidement par simple modification de la configuration des multiplexeurs. Dans la première partie de ce travail nous nous consacrons à l'analyse d'une telle architecture à fort potentiel. Une partie de sa structure est réalisée en technologie conventionnelle BiCMOS afin de valider sa faisabilité ainsi que le fonctionnement des solutions schématiques développées. Grâce à la caractérisation des composants, une analyse de la structure complète est réalisée. Cependant, la complexité de la structure du synthétiseur proposé fait de sorte qu'il existe pour les fréquences générées un grand nombre de fréquences parasites qui induisent des interférences entre utilisateurs. La réduction de leurs effets sur la transmission est l'objet de la deuxième partie de notre travail. Deux solutions numériques de réduction des interférences sont proposées. Elles permettent de rendre le design de la partie analogique moins contraignant en allégeant le cahier des charges et nous ont ainsi permis de simplifier l'architecture du synthétiseur. / The aim of this thesis is to study the feasibility and the performances of a fast switching frequency synthesizer designed for high debit multi-band multi-user transmission and used in transmission systems requiring a low consumption and an easy IC integration. In this context, the use of the classical synthesizer structures does not apply and there is a need to develop new architectures capable of generating all the frequencies permanently. Thus, the switching between frequencies can be easily done by changing multiplexors' state.In the first part of this study, we focus on the analysis of such high potential OL architecture. The main part of the proposed structure is implemented in a conventional BiCMOS technology in order to validate its feasibility and the operation of the developed blocks. Thanks to the measurements of the OL components, a complete analysis of the synthesizer is made. However, the complexity of the architecture of the proposed synthesizer induces the generation of large number of parasitic frequencies, creating interferences between the active users. The reduction of their effect on the transmission is the subject of the second part of the manuscript. Two digital methods are proposed to reduce the interferences. Lowering the requirements on the analog part, they allow a simplified design. This property was used to reduce the complexity of the frequency synthesizer.

<p>This thesis presents a study on built-in type low profile and low volume mobile phone antennas. In a coupling element based antenna, the chassis is the main radiator and the antenna elements are the exciters for the wave modes at low frequency. The main work of this thesis is to demonstrate and investigate the performance of the coupling element based antenna and study a variety of cases with different physical lengths and different physical heights. The investigation is done by using simulators. The performance is evaluated by analyzing the impedance bandwidth and the efficiency. For the study, antenna prototypes integrating miniaturized matching circuits were modeled. Two antenna structure prototypes covering five frequency bands were manufactured and measured. The Measured results are presented and compared with simulations. Finally, the performance of the coupling element based antenna is compared with planar inverter-F antenna (PIFA) and discussed.</p>

This thesis presents a study on built-in type low profile and low volume mobile phone antennas. In a coupling element based antenna, the chassis is the main radiator and the antenna elements are the exciters for the wave modes at low frequency. The main work of this thesis is to demonstrate and investigate the performance of the coupling element based antenna and study a variety of cases with different physical lengths and different physical heights. The investigation is done by using simulators. The performance is evaluated by analyzing the impedance bandwidth and the efficiency. For the study, antenna prototypes integrating miniaturized matching circuits were modeled. Two antenna structure prototypes covering five frequency bands were manufactured and measured. The Measured results are presented and compared with simulations. Finally, the performance of the coupling element based antenna is compared with planar inverter-F antenna (PIFA) and discussed.