Gps Spreading Code Synchronization

GPS (Global Position System) is a new generation precise navigation satellite timing and ranging system. Researching on GPS is very useful and important, which can be used for GPS production development .Furthermore, researching on GPS is helpful to develop the Chinese maritial navigation and positioning standard.GPS PN (Pseurandom Noise) code synchronisition technology includes code acquisition and track technology, which is the key technology in GPS. Whether the synchronisition function is good or bad determines the positoning precision in GPS is high or low. Generally, code acquisition and track are called as coarse and precise synchronisition. A lot of specialists pay much attention in this field and write a lot of papers.The process of GPS PN code acquisition is a two-dimension lengthy searching process in time and frequency dimension. In GPS, P code has high code speed and long sequence period, so P code is very hard to be acquised. Nowadys, Direct P code acquisition technology is a very important and useful technology. After the process of acquisition, the system must transfer to track process. The function of track is achieved by code track loop and costas loop. How to design the code track loop and costas loop is very hard, because the loop must can track fast and have small track error. In this paper, based on the research about the two processes of GPS synchronisition, some work is done as follow:First, based on analyzing and contracting the ways referred by thesis and paper on GPS, this paper proposes a new CCPAZP-FFT way of direct acquisition of the GPS P(Y) code. CCPAZP-FFT is a way that uses FFT to achieve Circular Correlation by partition and zero padding (CCPAZP) and achieve frequency synchronisition. In this way, acquisition can be achieved very fast as it transfers two-dimensional search into parallel one-dimensional search. Also, CCPAZP-FFT can be easily implemented in real GPS project for its low need in hardware resource. In the end, this paper gives the simulation result and the implemention result.Second, based on analyzing the function and principles of GPS code track loop and Costas loop, this paper proposed a way to design the digital phase-lockde loop. Then, the simulations about code track loop and Costas loop are made in Systemview. Then, test on the FPGA digital signal processing board proves that the digital code track loop which is designed based on the way proposed in this paper can track the GPS signal well.The synchronisition ways proposed in this paper are all based on real project need. So it can be used in real GPS project, such as GPS receiver synchtonisition, GPS control and receiving base synchronisition.