Research On Synchronization Of Baseband Signal Based On The Compass

On a country’s political, economic, military, cultural and other fields of satellite navigation system plays a very important role, is of great significance to safeguard the interests of the state. The construction of Compass with global navigation and positioning capabilities, has a profound impact on China’s economic construction and national defense construction.The two generation Compass is a new generation of satellite navigation system which is developed by China stand on its’own. With the gradual improvement of the Compass, large-scale application of Compass user machine has entered a substantive stage. The baseband signal processing module is the core module of the Compass user machine, the function of it is mainly to complete the analog-to-digital conversion, digital down conversion,carrier extracted, carrier locked indication,PN code synchronization, signal de-spreading and judgments and so on.This paper mainly discusses the baseband signal processing algorithm based on Compass.First of all.this paper introduces the researched background and significance of the topic.Then combining the concept of the spread spectrum communication, the article introduces the working principle of Compass user machine.meanwhile introducing its signal structure and modulation methods. And then putting forward two new acquisition schemes in the several common acquisition algorithm of PN code.which can improve SNR well.and weak the carrier Doppler frequency shift. In addition,based on the Tong detection algorithm for the acquisition performance of the system are analyzed in detail. Finally discussing the carrier tracking algorithm.Using phase-locked loop (FLL)and frequency locked loop(FLL)combined with some auxiliary carrier tracking algorithm, Based on the carrier Doppler frequency shift track after comparing with a preset threshold, to realize the automatic switching between PLL and FLL. After verification it shows that the pseudo-code frequency fluctuation of carrier Doppler frequency shift is to be greatly offset.The theory analysis and simulation indicates that the proposed method is feasible, and it can achieve the expected design goals.