Conception et mise en oeuvre de module de controle de puissance et de generation de bruit pour conditionner les signaux RF d'un simulateur de constellation GPS et Galileo

Satellite radio navigation has received considerable interest during the 21st century. The most important advents in this sector are the new satellite positioning system of the European Union called Galileo and the modernization of the Unites States' Global Positionning System GPS. The combination of these different systems under the acronym GNSS (Global Navigation Satellite System) would allow reliable positioning and a high accuracy. This trend pushes the industry to design receivers able to handle the growing number of signals. These new products require validation procedures before the European system, Galileo becomes operational.The power control system has been developed to provide an accuracy of about 0.1 dB over a range of 40 dB for signals "L1 GPS, Galileo E1" at a frequency of 1575.42 MHz, "GPS L5, Galileo E5a" at 1176.45 MHz and the Galileo signal E5b at 1207.14 MHz. The power control system has been implemented by developing a printed circuit board and a two-way communication with the software that allows complete system management. The architecture has been carefully studied and implemented to allow flexibility and scalability. It allows the user to run multiple control modes namely "gain control", "automatic power control, "power calibration" and "time varying power control". The power control system has been tested and validated to give an accuracy of less than 0.1 dB over 40 dB for both basic modes of operation (gain control and automatic power control). The other two modes resulting from the latter give more features to the user of the simulator.To give the user a total control of signal quality, a white Gaussian noise generator has been implemented. It allows, in addition to the power control system, the ratio C/N0 control. A study on methods for generating such a white noise was made. The choice was a digital implementation in the FPGA which provides a flexibility and lower complexity compared to an analog approach. The white noise generator was developed with the Box-Muller method which has many advantages in the case of digital implementation. Its architecture has been optimized to reach the hardware resources constraints of FPGA. The white Gaussian noise is combined with the signals in the RF part and its power can be controlled by software. It has been tested and validated by a commercial receiver and receiver built within the school. The linear increase in the noise level degrades the signal quality and the C/N0 ratio decreases linearly in both test receivers.Key words: GNSS, power control, white Gaussian noise, FPGA.In this context, the laboratory LACIME is developing a GPS and Galileo signals simulator. This master's thesis presents the different parts of the simulator and a detailed design study of a power control system driven by software for GPS and Galileo signals and a C/N0 ratio control system.