An optimized FFT based accquisition method for GPS receivers

AN OPTIMIZED FFT BASED ACQUISITION METHOD FOR GPS RECEIVERS ABSTRACT Global Navigation Satellite Systems (GNSS) provides worldwide continuous accurate position, velocity and time information to civilian and military users. This kind of access enabled usage of GNSS at various applications ranges from agriculture to finance. The most commonly known and used navigation satellite system is Global Positioning System (GPS) provided by USA. Glonass (Russia), Galileo (European Union), BeiDou (China) are the other types of GNSS. Each GNSS has different signals designed for different purposes. Therefore, flexible solutions should be implemented to handle these diverse signals. GNSS Software Defined Radio (SDR) answers this problem in terms of flexibility, modularity and upgradability. GNSS receiver, which is used in this work, is a multi-constellation, multi frequency SDR developed by TÜBİTAK SAGE. This thesis presents the implementation of the aforementioned SDR limited to GPS L1 signal. The SDR was built using FPGA and microprocessor for real time implementation. Acquisition and tracking are the main tasks which consume the most processing power for SDR solutions. Besides SDR, a novel optimized FFT based acquisition method is proposed in order to reduce acquisition process load.