Be connected to broadband WEB in flight is a trade issue which has motivated the launch of a project named FAST (Fiber-like Aircraft Satellite Communications). Under this project, Axess-Europe company with seven other partners including LAAS-CNRS, worked on the design of an active phased-array antenna with an electronically controlled beam steering. This thesis deals with the frequency synthesis of the antenna transceiver. In order to be able to connect to different satellites with their own frequency map, and also compensate for the Doppler effect to a certain extent, this focuses on the increase of the frequency resolution of a PLL (Phase-Locked Loop) using a fractional-N frequency divider. When considering a PLL, a fractional-N divider offers several advantages: increase frequency resolution without decreasing the reference frequency, and thus allows to keep the loop dynamic, as well as bandwidth and phase noise performances. However, fractional-N division generates spurious, which can yet be reduced by different well known techniques. Among these techniques, the DDS (Direct Digital Synthesizer) can be used as a fractional-N divider, but the increase of its frequency resolution would dramatically increase its size. So we designed a variant DDS-based topology, which allows to keep the advantage of the DDS in spurious reduction while increasing its frequency resolution without increasing its size. A comprehensive study of this novel structure is proposed.
