Two main topics are investigated in this dissertation: the analysis and design of an high efficiency power amplifier based on Load Pull measurement is first presented, followed by the design of a small antenna for a specific application of ocean monitoring. Due to the desire for lighter and longer lasting wireless devices, the need for efficient power amplifiers has become apparent and high efficiency greatly increases the life of battery by consuming less DC power for the same level of useful output power. The efficiency of an inverse class-F power amplifier will be explored in this document. A load- and source-pull system are used to achieve the best performance in terms of efficiency for the specific device considered since they allow to know the best load and source to be placed at the drain and the gate of the transistor respectively. Theoretical backgrounds are first presented both for power amplifiers in general and for the Inverse class F. In the following chapter multi-harmonic matching networks are analyzed and designed as well and results are presented. A real load-pull system, described in the first chapter, has been used in this work although correct measurements has not been achieved. Results presented therefore derives from simulations.

The second part deals with the design of a small antenna to be used in a smart sensor and to monitor oceanic floor. Difficult parts of this project are related with the very small room available for the antenna and with the enclosure material that wraps the sensor, in particular with its electrical properties. Both the application and all problems related with it are described and analyzed in the first chapter of the second part and all designs considered in order to meet specifications are discussed in the following one. The enclosure material is analyzed as well as a fundamental part of the system. The last chapter presents achieved results and future steps.