Research And FPGA Implementation Of Beidou Baseband Signal Acquisition Algorithm

Beidou satellite navigation system,independently developed and operated in China,has officially and successfully provided positioning services worldwide,which significantly promotes the satellite navigation application industry and creates tremendous social and economic benefits.Signal acquisition is a crucial first step in the baseband signal processing of the Beidou receiver,and its main task is to assess and estimate the carrier frequency and the code delay so as to initialize the tracking loop.The signal acquisition requires searching in three-dimensions leading to massive digital signal processing and complex logic control,as a result,the quality of the acquisition performance will directly affect the navigation processing speed and accuracy of the receiver.Hence,the techniques to improve the performance of acquisition has become a research hotspot in recent years.This paper first elaborates the positioning principle of the Beidou satellite navigation system,then analyzes and compares three baseband signal acquisition algorithms.The time domain parallel search acquisition algorithm is primarily chosen for further study considering its speed advantage,and an improved quadratic function fitting-based acquisition method is proposed.In this method,the correlation results generated during signal acquisition are used as the fitting data set,and the high-precision carrier frequency is quickly worked out by quadratic function fitting.The function and performance of the proposed approach are simulated in Matlab,and the feasibility of the algorithm is verified thereafter.In the next step,the hardware circuits of the acquisition method are designed using Verilog hardware description language,and the functional verifications of each module along with the entire system are performed with the help of Modelsim.Lastly,the board-level test is completed on the Altera DE4-SoC development board,which validates this improved acquisition system design.The Matlab simulation and board level test results show that,compared with the traditional time domain parallel search acquisition algorithm,the improved acquisition algorithm increases the carrier frequency acquisition accuracy by 21%when the acquisition time is similar.