High Dynamic Spread-spectrum Signal Fast Acquisition Method

Nabigation Positioning Ststem(NPS) can be used to offer the Nabigation Positioning Service for the conveyanve of road,railway ,the air and the sea.It can be uesd for army and civilian,and it has traffic function and business behalf.It consists of several secondary planets,wich go around the earch and the blaze away wireless signal.No matter where you are,on the land ,in the sea or in the air,if only you have a receiver on hand,you can receive the signal eradiated by the secondary planet.The computer in the receiver choose several swalth ti analysee,in this way,you can make sure where you are.Compared to other communication technologies, Spread Spectrum(SS) technology has the advantages of low probability of intercepting, a high immunity to interference, hiding the useful information and multiple-access communication ability. In modern information times, it has been one of the three high-technological communication means and is developing from military use to commercial environment. In this dissertation, the author mostly research on Direct Sequence Spread Spectrum (DS-SS), the most ordinary one within Spread Spectrum technologies.Fast acquisition process of spread spectrum signals is crucial in direct sequence spread spectrum (DS-SS) communications. The acquisition process has to search both carrier frequency Doppler shift and PN code phase, so the whole acquisition process is a two-dimensional search process. The high dynamic spread spectrum signals include high Doppler shifts which may exceed 100 kHz, largely increases the difficulties of acquisition process. Compared to traditional acquisition method, this dissertation utilizes an FFT-based partial correlation by partition and zero padding acquisition method to search the correct code phase and estimate the carrier Doppler shifts simultaneously. By using this method, the former two-dimensional acquisition process becomes a one-dimensional process and reduces the acquisition time.The structure and the performance of the FFT-based partial correlation by partition and zero padding acquisition method are analyzed and several ways are proposed to improve the method in this dissertation. The performance of the method is simulated in this dissertation and the simulation results show that the method can efficiently perform the acquisition process of the high dynamic spread spectrum signals.In this dissertation, the P code acquisition is realized in FPGA. The research result of this dissertation can be applied in the high dynamic satellite navigation receiver as well as the ordinary satellite navigation receiver.