Fast Acquisition Of Weak Signal In High Dynamic Environment

Spread Spectrum communication has strong advantages on anti-jamming, CDMA and high precision measure in Wireless navigation system. However, under low SNR and high dynamic environment which has high real time requirement, it's very difficult to complete fast acquisition of Spread Spectrum code.This paper analyzed many domestic and international interrelated literatures and research papers which concern about fast acquisition of weak signal in recent years. The problems about how to get initial Doppler Frequency value and code phase have been argued. A new technique named Extended Replica Folding Acquisition Search Technique (XFAST) has been introduced to the application of weak signal's fast acquisition. And the module of signal acquisition is implemented based on FPGA platform.The research work in this paper mainly includes the following several respects.Firstly, the paper analyzed basic principle of Spread Spectrum communication, and the principle of signal acquisition and tracking. Base on FFT signal acquisition technique, Extended Replica Folding Acquisition Search Technique (XFAST) has been introduced.Secondly, Extended Replica Folding Acquisition Search Technique (XFAST) has been employed to the application of weak signal's fast acquisition. Compares to FFT acquisition technique, the differences and advantages by using XFAST has been analyzed from practical and theoretical aspects.Thirdly, weak signal's fast acquisition in high dynamic environment has been implemented base on FPGA hardware platform. The signal acquisition module is implemented by xc2v3000 which is developed by Xilinx.In conclusion, the paper proposed a new technique which employs XFAST for the application of weak signal's fast acquisition. This method not only avoids consuming large hardware resource in other acquisition techniques but also inherits the advantage of using frequency searching instead of timing searching, enhances the ability of weak signal's fast acquisition. The implemented result shows that we just need 248us ms to finish weak signal's fast acquisition once. It improves the speed of acquisition obviously and satisfies the requirement of real time acquisition of signal.