Research On The Acquisition Algorithm Of High Dynamic And Weak GPS Signal

Recent years, GPS navigation technique plays a more and more important role in transportation, GIS and resource survey. So research on GPS navigation related technique is caught in a craze by many institutions and enterprises. GPS hardware receiver is applied because of ASIC rapid development. But it is not programmable and flexible. Different from hardware receiver, signal acquisition and tracking are accomplished by software in software receiver. Software can test influences of different algorithms on the performance of receiver, so software receiver provides fast analysis and verification on the algorithms for us. Many methods on signal acquisition in software receiver are presented in order to acquire signals in weak signal or highly dynamic environments. Additionally, traditional methods are improved. The efficiency of the methods is proved by simulation. The main work of the paper includes:1. Generally introduces three modules in software receiver, they are: RF front-end, signal processing and positioning calculation. Signal tracking is introduced as the part of signal processing. The structure of GPS signal is introduced. Especially, the properties of spread spectrum code, C/A code, are given a detailed introduction. The methods based on serial search and FFT search are recommended. Best data combination acquisition as a new method is presented. Coherent integration takes the place of incoherent integration in this method in order to improve sensitivity of receiver. A fast acquisition method based on cross-relation properties of C/A code. Improvement on this method can resolve ambiguity of results.2. Batch processing acquisition method based on FFT search is presented. Best data combination method and Batch processing method are used to acquire static, weak signals generated by SPIRENT 8000. The results of two methods are analyzed as a comparison.3. Based on the introduction of the structure of tightly integration navigation system GPS/INS and the theory of frequency compensation, a preprocessing method on highly dynamic signals is presented. With preprocessing stage, the results of acquisition are analyzed and summarized.The paper has particularly analyzed the theory of best data combination acquisition method based on the research of traditional acquisition methods. The method is used to test feasibility under two different conditions. The discussion on the results of acquisition is launched. The work in the paper lays the foundation of thorough study in modern GPS software receiver.