No description available.

Ce travail répond à un besoin industriel accru en termes d’amplification des signaux sur porteuses à enveloppes variables utilisés par les systèmes de télécommunications actuels. Ces signaux disposent d’un fort PAPR et d’une distribution statistique d’enveloppe centrée en-deçà de la valeur crête d’enveloppe. La raison pour laquelle les industriels télécoms requièrent alors des amplificateurs de très fortes puissances de sortie, robustes, fiables et ayant une dépense énergétique optimale le long de la dynamique d’enveloppe associée à un niveau de linéarité acceptable. Ce document expose les résultats d’étude et de réalisation de deux Amplificateurs de Puissance Doherty (APD) à haut rendement encapsulés en boîtiers plastiques QFN. Le premier est un amplificateur Doherty symétrique classique (APD-SE) et le second est un amplificateur à deux entrées RF (APD-DE). Ces démonstrateurs fonctionnant en bande C sont fondés sur l’utilisation de la technologie Quasi-MMIC associant des barrettes de puissance à base des transistors HEMTs AlGaN/GaN sur SiC à des circuits d’adaptation en technologie ULRC. L’approche Quasi-MMIC associée à la solution d’encapsulation plastique QFN permettant une meilleure gestion des comportements thermiques offre des performances électriques similaires à celles de la technologie MMIC avec des coûts et des cycles de fabrication très attractifs. Durant ces travaux, une nouvelle méthode d’évaluation des transistors dédiés à la conception d’amplificateurs Doherty a été développée et mise en oeuvre. L’utilisation intensive des simulations électromagnétiques 2.5D et 3D a permis de bien prendre en compte les effets de couplages entre les différents circuits dans l’environnement du boîtier QFN. Les résultats des tests des amplificateurs réalisés fonctionnant sur une bande de 1GHz ont permis de valider la méthode de conception et ont montré que les concepts avancés associés à l’approche Quasi-MMIC ainsi qu’à des technologies d’encapsulation plastique, peuvent générer des fonctions micro-ondes innovantes. Les caractérisations de l’APD-DE ont relevé l’intérêt inhérent à la préformation des signaux d’excitation et des points de polarisation de chaque étage de l’amplificateur. / This work responds to an increased industrial need for on carrier signals with variable envelope amplification used by current telecommunications systems. These signals have a strong PAPR and an envelope statistical distribution centred below the envelope peak value, the reason why the telecom industrialists then require a robust and reliable high power amplifiers having an energy expenditure along of the envelope dynamics associated with an acceptable level of linearity. This document presents the results of the study and realization of two, high efficiency, Doherty Power Amplifiers (DPA) encapsulated in QFN plastic packages. The first is a conventional Doherty power Amplifier (DPA-SE) and the second is a dual-input Doherty power amplifier (DPA-DE). These C-band demonstrators are based on the use of Quasi-MMIC technology combining power bars based on the AlGaN/GaN transistors on SiC to matching circuits in ULRC technology. The Quasi-MMIC approach combined with Quasi-MMIC approach combined with QFN plastic package solution for better thermal behaviour management offers electrical performances similar to those of MMIC technology with very attractive coasts and manufacturing cycles. During this work, a new evaluation method for the transistors dedicated to the design of DPA was developed and implemented. The intensive use of 2.5D and 3D electromagnetic simulations made it possible to take into account the coupling effects existing between the different circuits in the QFN package environment. The results of the tests of the amplifiers realised and operating on 1GHz bandwidth validated the design method and showed that the advanced concepts associated with the Quasi-MMIC approach as well as plastic encapsulation technologies can generate innovative microwave functions. The characterizations of the DPA-DE have noted the interest inherent in the preformation of the excitation signals and the bias points of each stage of the amplifier.

The ever increasing diversity in communication systems has created a demand for constant improvements in receiver components. This thesis describes the design and characterisation of front-end receiver components for various challenging applications, including characterisation of low noise foundry processes, LNA design and multi-band antenna design. It also includes a new theoretical analysis of noise coupling in low noise phased array receivers.In LNA design much depends on the choice of the optimum active devices. A comprehensive survey of the performance of low noise transistors is therefore extremely beneficial. To this end a comparison of the DC, small-signal and noise behaviours of 10 state-of-the-art GaAs and InP based pHEMT and mHEMT low noise processes has been carried out. Their suitability in LNA designs has been determined, with emphasis on the SKA project. This work is part of the first known detailed investigation of this kind. Results indicate the superiority of mature GaAs-based pHEMT processes, and highlight problems associated with the studied mHEMT processes. Two of the more promising processes have then been used to design C-band and UHF-band MMIC LNAs. A new theoretical analysis of coupled noise between antenna elements of a low noise phased array receiver has been carried out. Results of the noise wave analysis, based on fundamental principles of noisy networks, suggest that the coupled noise contribution to system noise temperatures should be smaller than had previously been suggested for systems like the SKA. The principles are applicable to any phased array receiver. Finally, a multi-band antenna has been designed and fabricated for a severe operating environment, covering the three extremely crowded frequency bands, the 2.1 GHz UMTS, the 2.4 GHz ISM and the 5.8 GHz ISM bands. Measurements have demonstrated excellent performance, exceeding that of equivalent commercial antennas aimed at similar applications.