The Design And Simulation Of GNSS Receiver P Code Rapid Acqusition Channels

Satillaite Navigation has been applied wildly in many fields. Today ongoing GNSSs include GPS of U.S, BDS II of China and GLONASS of Rassuia. GPS and BDS II are code division multiple access(CDMA) systems, while GLONASS is frequence division multiple access(FDMA) system. CDMA systems can increace the positioning percision and enlarge the noise tolerance through using long period codes. Therefor GPS and BDS II all have long period codes which are kown as P codes. Although P code has its advantages, its extreamly long period makes it very hard to acqusite and needs more time. On the other hand, because P codes are mostly used in aviation, arospace and militery field where the applications of P code receivers need to be able to acqusite rapidly under high dynamic enviroment, which will certainly increase the difficulties and time. So P code receivers have very high requirements on acquisition algorithm.This thesis fouses on the dsign of P code rapid aqusition channels under high dynamic enviroment. Firstly, the signal models, characteristic and structure of P code, Doppler Effect, coherent and non-coherent aqusition principles are introduced.Sencondly, theory of FFT-based circular correlation and theory of multiple partial macthed filters combined with FFT are presented. After the analysis of their principles and characteristic is performed, the later one is selected by comparision.Thirdly, the relation of coherent time and coherent gain is introduced. The influence of high dynamic upon signals and FFT is presented. In order to expand the amplitude frequency characteristic of the channels, a scheme of applying multiple parallel acqusition channels with frquencey copemsation is put forward. And in order to improve the resolution of frequence detection, a method of applying a long time matched filter is discussed. After that simulations of the design is performed.Finally, the P code generator module and the matched filters are realised by VHDL coding. While the folding scheme of filters realisation will reduce the cost of resouces. Modules are verified by cosimulation of Matlab and Model Sim.The analysis of P code acquisition under high dynamic enviroment could be used to instruct the receiver design, and simluations could verify the results, while VHDL realizations make the desgin more practical. Although there is no on-board debugging, the theory analysis, co-simulation and code verifying could also be helpful to the development of P code receiver.