Research On Acquisition Algorithm In Beidou B2a Signal And Implementation On FPGA

At present,the global deployment of the Beidou-3 navigation satellite system(BDS-3)has been fully completed.As a new civil signal added in BDS-3,B2 a signal includes data and pilot component,and uses hierarchical code structure,which increases the difficulty of receiver signal processing.As the primary work of baseband signal processing,signal acquisition performance directly affects signal tracking accuracy and loop convergence speed.Therefore,it is of great practical importance to promote the acquisition speed and accuracy for navigation receiver.Taking the B2 a signal as the research object,the baseband acquisition algorithm of B2 a signal and FPGA implementation are completed.Firstly,the structure and characteristics of B2 a signal are described in three aspects: signal carrier,ranging code and navigation message.In addition,the acquisition principle of satellite navigation signal is researched,and B2 a signal acquisition is simulated by three traditional acquisition algorithms.Secondly,the B2 a signal acquisition algorithm is proposed based on the combination of Partial Matched Filtering and Fast Fourier Transform(PMF-FFT),and it can be easily applied to engineering.By analyzing the influence of chip delay and carrier frequency offset,the PMF-FFT parameters are determined including PMF segment length,FFT operation points,coherent integration time and incoherent integration times.The PMF-FFT acquisition algorithm is simulated,and its performance indexes are analyzed including acquisition time,acquisition accuracy and acquisition probability.Then,according to the characteristics of PMF-FFT acquisition algorithm,a design scheme of hardware and software collaboration was proposed,and the engineering implementation of the acquisition algorithm is completed on Zynq platform.The implementation scheme mainly includes PL-PS signal interaction,PS-based acquisition strategy and PL-based acquisition logic.Among them,the PL-based scheme includes control core module,data preprocessing module,pseudo code generation module,partial matching filter module,FFT module and threshold judgment module.Finally,the function of key modules are verified by the Vivado tool,and the system test for real B2 a signal acquisition is mainly completed on Zynq platform.The results show that PMF-FFT algorithm can effectively acquire B2 a signal and has good performance.It saves a lot of logic resources in hardware implementation and has certain application prospects and reference value.