| The satellite navigation application industry has become a global high-tech industry and an indispensable part of our daily lives.It is commonly used in transportation,high-precision measurement,military applications,etc.At the same time,users have raised questions about the timeliness of navigation.With higher and higher requirements,the simulation and rapid capture of navigation signals has become an important research content.Firstly,this paper introduces the composition of the Beidou navigation system,including its coordinated system and time system and the conversion between them and other coordinated system and time system,as well as the specific structure of the Beidou B1 I signal,and describing the generation process and the modulation process of the signal in the aspects of carrier,pseudo-random code and data code.Secondly,this paper studies the advantage of the principle of Spread Spectrum Communication used to Beidou navigation system and the acquasion principle of Beidou navigation signal.It studies and comparies the theories of the traditional serial time domain search capture,parallel frequency search capture,parallel code phase search capture and matched filter capture are studied and simulated,analyzes the characteristic of them and finishes the simulation and verification by Matlab.Finally,the Beidou navigation signal system is established based on Simulink,and the signal can be changed by changing the setting of pseudo-random.On the basis of the verification and analysis of the traditional acquisition algorithm,this paper studies the modified PMF-FFT algorithm.By windowing,the scalloping loss of PMF-FFT is reduced.The received signal passes through multiple matched filters in parallel and the result is subjected to FFT operation,which can make it come true,that the frequency and code phase is searched parallelly.The algorithm improves the performance of acquisition algorithm,including the detection probability is improved and the capture time is reduced. |
