Research On GNSS Signal Receiver Algorithms

With the widespread use of the Global Positioning System (GPS), more and more mobile terminal are equipped with GPS receiver modules. Diversity of receiver and its application also proposed new requirements for receiving GPS satellite signals: high dynamic receiver for high-speed mobile terminal, ultra-low signal to noise ratio for weak signal reception, and even multi-path for indoor reception. Receiver should meet these needs.GPS satellite signal is modulated using direct sequence spread spectrum (DSSS), has a strong immunity and confidentiality under the transmission. Its requirements for the receiver is to maintain a high phase synchronization; received satellite signals will be with a large Doppler shifting, the received carrier frequency has a offset from the central carrier, which will bring series of problems for the signal carrier demodulation. Technology to solve these two problems comes down to synchronization. A GPS signal reception process includes signal detection, signal acquisition and signal tracking.This study focuses on GPS signal acquisition, made an in-depth study of the GPS signal reception, especially acquisition algorithms, focused on the fast Fourier transform (FFT) algorithm. A series of improvements or additions to the algorithm was proposed by analyzing and comparing a variety of acquisition algorithm and the theoretical analysis. Matlab platform was used to build a simulation environment for the algorithm simulation and verification. It also simulated the high dynamic and low Signal to Noise Ratio (SNR) environment for new features of the GPS applications. Simulation results show the effectiveness of some algorithms and feasibility of the algorithm, as well provides a wealth data for improvements of the algorithm.