Anti-jamming Gps Signal Acquisition And Doppler Prediction Method

Two methods in ensure and enhance GPS acquisition performance have been studied in this thesis.The acquisition process needs long sequence of correlating accumulation for weak GPS signals. In order to limit the hardware scale and power consumption of signal process unit, the base band signal has to be quantized with low bit. In the same time, GPS signals are vulnerable to interferences, either unintentional or intentional. Among these interferences, the narrow band continuous wave (CW) is the most common type. Signal to noise ratio (SNR) in traditional quantizer with fixed quantizing levels degrades rapidly in the presents of CW interference. As a result subsequent processes lose the chance of getting proper correlation peak.Based on the theory and experiment results of nonlinear adaptive A/D converter, a method of re-quantizing has been analyzed and simulated. It has been proved the method is able to suppress CW interference significantly.The Doppler of GPS signal is dominated by satellite's position and velocity, as well as the receiver's position and velocity. The receiver's position can be estimated while receiver's velocity can be necessarily compensated by external equipments. The method of deriving satellite's position and velocity from ephemeris has been proposed; with which Doppler of the signal from certain satellite can be calculated. Thus the acquisition process shrinks its range of Doppler search, hence the acquisition time can be reduced, especially for cold-start receiver.