Ces travaux de recherche concernent les amplificateurs RF de puissance pour stations de base. La technologie actuelle de transistor RF la plus compétitive, le LDMOS, est confrontée à l’augmentation constante du débit et à la concurrence d’autres technologies comme le HEMT GaN. Un autre challenge est l’intégration de l’adaptation de sortie réalisée en dehors du boîtier qui n’est plus compatible avec les futurs standards combinant jusqu’à soixante-quatre amplificateurs de puissance proches les uns des autres.Une première piste envisagée dans cette thèse est le substrat Si à haute résistivité. A partir de simulations puis de mesures sur plaques, l’amélioration du facteur de qualité des éléments passifs a été démontrée mais ces premières investigations ne permettent pas l’intégration de l’adaptation de sortie avec la technologie actuelle bien que les résultats soient très encourageants. Les challenges technologiques de ce nouveau substrat ont mené à considérer la structure différentielle pour les amplificateurs. En plus des avantages connus de cette configuration, nous avons montré que la conception d’un amplificateur de puissance différentiel montre une amélioration importante de la bande instantanée répondant au besoin d’un débit toujours plus élevé. Cette amélioration ne dégrade pas les autres performances en gain, rendement et puissance de sortie. Dans la continuité de cette thèse, les perspectives concernent la conception d’un amplificateur de puissance sur substrat SI à haute résistivité combinée à une structure différentielle qui pourrait permettre une avancée majeure sur toutes les performances tout en gardant l’avantage du faible coût du LDMOS Silicium en comparaison des autres substrats. / This research concerns the RF power amplifiers for base stations. The current most competitive technology of RF transistor, the LDMOS, faces the constantly increasing data rate and competition from other technologies such as GaN HEMT. Another challenge is the integration of the output matching made outside of the package which is not compatible with future standards combining up to sixty-four power amplifiers close to each other. A first track proposed in this thesis is the high resistivity Si substrate. From simulations and measurements on wafers, improved passive elements quality factor has been demonstrated but these initial investigations do not allow the integration of the output matching with the current technology, although the results are very encouraging. The technological challenges of this new substrate led to consider the differential structure for amplifiers. Besides to the known advantages of this configuration, we have shown that the design of a differential power amplifier shows a significant improvement in the instantaneous band width meeting the need for higher data rate. This improvement does not degrade other performance as gain, efficiency and output power. In continuation of this thesis, the perspective concerns the design of a power amplifier on a high resistivity Si substrate combined with a differential structure that could enable a major advance over all performance while keeping the advantage of low cost of LDMOS silicon compared to other substrates.

The quadratic class of time-frequency distributions (TFDs) forms a set of tools which allow to effectively extract important information from a nonstationary signal. To determine which TFD best represents the given signal, it is a common practice to visually compare different TFDs' time-frequency plots, and select as best the TFD with the most appealing plot. This visual comparison is not only subjective, but also difficult and unreliable especially when signal components are closely-spaced in the time-frequency plane. To objectively compare TFDs, a quantitative performance measure should be used. Several measures of concentration/complexity have been proposed in the literature. However, those measures by being derived with certain theoretical assumptions about TFDs are generally not suitable for the TFD selection problem encountered in practical applications. The non-existence of practically-valuable measures for TFDs' resolution comparison, and hence the non-existence of methodologies for the signal optimal TFD selection, has significantly limited the use of time-frequency tools in practice. In this thesis, by extending and complementing the concept of spectral resolution to the case of nonstationary signals, and by redefining the set of TFDs' properties desirable for practical applications, we define an objective measure to quantify the quality of TFDs. This local measure of TFDs' resolution performance combines all important signal time-varying parameters, along with TFDs' characteristics that influence their resolution. Methodologies for automatically selecting a TFD which best suits a given signal, including real-life signals, are also developed. The optimisation of the resolution performances of TFDs, by modifying their kernel filter parameters to enhance the TFDs' resolution capabilities, is an important prerequisite in satisfying any additional application-specific requirements by the TFDs. The resolution performance measure and the accompanying TFDs' comparison criteria allow to improve procedures for designing high-resolution quadratic TFDs for practical time-frequency analysis. The separable kernel TFDs, designed in this way, are shown to best resolve closely-spaced components for various classes of synthetic and real-life signals that we have analysed.