Design and Implementation of Multi-Frequency GNSS Receiver Using Direct RF Sampling

Multi-Frequency GNSS receiver using direct RF sampling is designed and implemented to solve defects existing in analog RF front-end, which places the analog digital convertor behind the antenna to digitize the signal in RF domain leaving the rest of signal processing implemented in software module. This special receiver could be adapted to GNSS signal from different navigation system by simply parameter setting and is very convenient for upgrading and updating. Multi-frequency front end is designed to accommodate the public navigation bands. The key techniques is analyzed in detail including sampling frequency design, local oscillator selection, decimate and filtering. The receiver architecture is presented based on SoPC (System on Programmable Chip). The implementation diagrams and sequences of function modules are analyzed. Test using GNSS simulator is operated to evaluate the performance of this new receiver.