Research On Receiving Algorithm Of GNSS Signal And Implementation On FPGA

The satellite navigation industry is a rapidly developing information industry following the Internet and Mobile Communication. The technology of GNSS signal reception, which plays an important role in the development of the navigation system, is an important part of the navigation industry. The civil signal of GPS and MBOC signal of Galileo are chosen as the object of research in this paper. The performance of the quick acquisition and tracking algorthom is investigated and a certain flexibile GPS receiver system is designed based FPGA.1) To research the nature and integration of the GPS L1-band signal and Galileo E1 band MBOC signal, the autocorrelation function and power spectrum function are analyzed. This is the foundation of quick acquisition and tracking.According to signal detection and estimation theory, we get the principle of signal acquisition. Frequency domain method is used to capture GPS signals and Galileo signals. To reduce the edge peak on the impact of the Galileo signal acquisition, some algorithms are realized in the frequency domain. The experimental results show that the system can achieve strong acquisition probability2) By the analyzation on GNSS signal structure, three fast acquisition algorithms are desgined.The first acquisition method is based on differential folding matched filter and FFT algorithm with small points to get the code phase and Doppler frequency. The signal to noise ratio is improved by the quick acquisition algorthom using the principle of pre-processing, and we desgin different acquisition algorithm for different strength signal. The improved frequency acquisition algorithm using double thresholds can improve the acquisition speed.3) The single-frequency interference may affect the GNSS signal, and anti-jamming frequency domain algorithm is also discussed in this paper. Using the analog output of the GP2015 and AD9433 to adjust the sample resolution, the sample bits are transferred into FPGA and the improved frequency acquisition algorithm are implemented in FPGA.Then, the tracking loop for GPS and Galileo signals are investigated, particularly for code tracking loop. For multi-peak problem of Galileo signal, several new code phase detectors are discussed. Finally, we design the tracking loop based FPGA, obtain simulation results in modelsim and get actual results in the oscilloscope.