Research On Acquisition And Trace Of Spread Spectrum Signal In High Dynamic Circumstances

Spread-spectrum technology is applied widely in the field of satellite navigation. The synchronization of spread-spectrum signal is the key issue of spread-spectrum technology, which includes acquisition and tracking of spread-spectrum signal. The process of Spread spectrum signal acquisition not only embody the acquisition of carrier frequency, but also the acquisition of PN-code phase. The locomotive-velocity and its derivative of carrier under the high dynamic environment often range dramatically, which leads to hundreds of kHz Doppler frequency shift of Spread-spectrum signal. It makes the acquisition and tracking more difficultly.Based on the research in depth about the primitive algorithm of acquisition and tracking ,this paper analyze the key issue of the acquisition and tracking of Spread-spectrum signal under the high dynamic environment theoretically, and put forward a scheme which adapt to acquisition and tracking of Spread-spectrum signal under the high dynamic environment. The simulation of the scheme and the implement of partial module with FPGA are set up at length.Firstly, Via thorough theoretical analysis and research about various acquisition algorithm, a new scheme that combine delay-superposition with coherent-accumulation based on PMF is proposed for points of claim about the high dynamic environment. And then the performance is verified.Secondly, referring several algorithm of typical signal parameter estimation and the particularity of high dynamic environment, the AFC is chosen as the basic algorithm of tracking loop. PN-code tracking loop which is based on carrier tracking loop adapt to non-coherent DLL. Carrier tracking loop is composed of Four-quadrant Frequency Discriminator, CPAFC and Costas. Some simulation is given with Matlab.Finally, based on the theoretical analysis above, the FPGA design and function simulation on several central units of spread-spectrum signal synchronization module.