Research On Carrier Tracking Technology Of High Dynamic GNSS Signal

Navigation guidance has occupied a very important position in modern warfare.If you can get the advanced of navigation guidance technology,therefore,you can get an incomparable opporunity to win it.Thus,each country takes more and more attention on the research of the GNSS signals synchronous technology in high dynamic conditions. Under high dynamic conditions, GNSS signal is superimposed larger Doppler shift, and if using conventional GNSS navigation signal receiver, the Doppler shift can not be locked that has a greater impact on the positioning of the latter. Thus, GNSS carrier tracking technology will be of great practical significance under high dynamic conditions of this study. Main research contents as follows:1、Because of the impact on carrier tracking of high dynamic environment and the weaknesses and strengths on tracking in a highly dynamic environment of PLL and FLL,the third-order PLL and second-order FLL are combined in order to complete carrier tracking.During the tarcking, a threshold is used to determine which loop is switchen between FLL and PLL. From the simulation results,it can be seen after the loop track,doppler frequency fluctuations can be locked in short time. But in the loop switching process, there will be hopping phenomenon which coase a large tracking error and easy to cause the loop loses lock.2、By analyzing the limitations of threshold-based discrimination FLL / PLL and advantages of Kalman filter on the carrier tracking, this article designed a high dynamic carrier tracking loop of FLL&PLL which is based Kalman filter. The new Loop combines the two filter of FLL and PLL and ensure those two loops working tergther. Then the results of the PLL is processed by Kalman filter, in order to increase the accuracy of the results. The simulation results of tracking in the zero-noise conditions has proved tha the new loop can tracking the doppler stably and avoid the frequency hopping phenomenon because of FLL and PLL switched; The loops’ performance of tracking is simulated under different carrier to noise ratio conditions, and comparied the RMS error with the old loop. Reference loop does improve the accuracy of tracking has certain advantages.3、This articles designed another high dynamic carrier tracking loop based on prediction and pre-compensation algorithm by studying the weighted recursive least squares algorithm and phase unwrapping algorithms; The main idea of this loop is: the prediction result which is the next output of the phase detector of the loop is compensated to the next output of carrier NCO and the phase detector to reduce the dynamic phase of the output of the phase detector and the reinforcing robustness noise. Through simulation analysis, the loop has a certain nature.