Design optimization of a direct radio frequency sampling multi-GNSS receiver front end

The recent development in satellite navigation systems is experiencing a meteoric rise with the releases of the European and Chinese systems, and its already competing with the existing American and Russian positioning systems. GNSS receivers will have to adapt to a multitude of signals at different frequencies or from different constellations. To achieve that in a traditional way, several receivers front-ends are required for each GNSS receiver. This approach quickly becomes complex and expensive for multi-frequency receivers. A new and elegant approach is proposed to overcome this issue by using direct RF sampling technique that samples all signals simultaneously and process them digitally afterwards. This approach greatly reduces the hardware requirement in the traditional receiver by placing the analog to digital converter as close as possible to the antenna and eliminating the mixer (analog RF) stages. The lack of theoretical contribution in the li terature has been the main motive for this study. The thesis aims to introduce a complete theoretical framework on direct sampling RF receiver, followed by simulation and correlation between theoretical and simulation results A part of the theoretical framework , a new approach of a simplified sampling frequency selection algorithm s is proposed for the single and multiple bands while as well as analyzing and modeling the relationship between system noise and the sampling frequency. In the simulation part, a DRFS receiver for the GPS L1 C/A signal is considered . The RF Filters limits the signal capture with band of 15 MHz around the L1 Frequency. Finally, The sampling stage is done using a several sampling frequencies of (30.1217 𝑀𝐻𝑧, 90.365 𝑀𝐻𝑧, 203.321 𝑀𝐻𝑧) followed by correlations to verify the effect of the sampling frequency on the RF signal spectrum as well as the system noise.