Navigation Receiver Time And Frequency Synchronization Technology And Performance Simulation

Satellite navigation system plays an important role in the national economy information-based construction as a significant basic facility, which directly counts much for economic development, national security and modernization of national defense. During recent years, as the technology kept being improved, the satellite navigation and positioning technique has developed towards property of hi- precision, hi- dynamic and anti- jamming. Navigation receivers belong to the users'equipments in the satellite navigation & positioning systems, which perform normally only when they can realize the time and frequency synchronization precisely. This dissertation investigates the topic of time and frequency synchronization technology for modern navigation receivers. The content of the dissertation is shown as following:The structure and modulation format as in American GPS receivers and how the navigation signals can be synchronized is introduced, this dissertation also points out the key techniques and difficulties as in time and frequency synchronization for modern navigation receivers by analyzing both new function and technique requirements in the complicated electromagnetism battle field environment.The precise code direct acquisition is a key practical engineering problem in the design of navigation receivers. This dissertation analyzes the difficulties and the main influence factors of this problem. An acquisition model is established and a parallel correlation structure based on FFT is designed by taking advantage of the FFT operation which is capable of compensating the peak value loss caused by Doppler frequency shift, the operation complexness and the acquisition time needed is analyzed as well.A second-order phase-locked loop is used to estimate carrier phase and Doppler frequency in the case of low dynamic situation. When the case of high dynamic situation is taken into consideration, a method of extend Kalman filtering is employed to estimate carrier phase and Doppler frequency, and the performance of PN code delay loop is improved by using carrier assist technique. An accurate PN code delay estimate and a good dynamic capability can be achieved. As most synchronization techniques of navigation receivers are adopted without considering the jamming environment, this dissertation also discusses the capability of synchronization techniques employed here in three different jamming environments by the software simulation.