Research On Acquisition Algorithms Of Satellite Signal For BDS

The signal processing of Beidou satellite navigation system generally goes through three stages:acquisition,tracking and calculation.The acquisition is not only the first stage of Beidou satellite signal processing,but also a key link.There are two problems in the acquisition of satellite signals:1.In the complex environments,the signal-to-noise ratio of signals is generally very low,which is not conducive to the separation of satellite signals from noise and difficult to capture.2.Satellite acquisition algorithm contains a large number of FFT operations.Without separate hardware acceleration,the cold start of software receiver will take a long time.This paper mainly studies the acquisition algorithm of Beidou satellite software receiver.And the solutions to the above two problems are given.The main research work and innovations include the following aspects:1.To solve the problem that NH code may jump every 1ms and affect the acquisition sensitivity of Beidou satellite signal,an improved coherent accumulation algorithm is proposed.By traversing the composition of data blocks of continuous signals,the correlation values larger than the threshold are found,and the effect of NH code hopping on signal accumulation is weakened.The simulation results show that the improved acquisition algorithm can reduce the impact of NH code hopping and improve the sensitivity of Beidou satellite receiver.Compared with the incoherent accumulation algorithm,the acquisition sensitivity is improved by about 2 dB.At the same time,the algorithm of cumulating first then correlating was used to reduce the complexity of the algorithm.2.A method of stripping NH code is proposed.Using the first acquisition results,the sampling values are matched completely,and the coherent accumulation algorithm is used after stripping the NH code.The algorithm can completely strip the NH code.At the cumulative length of 20 ms,it has about 4 dB improvement over incoherent cumulative algorithm,which improves the sensitivity of BDS software receiver.3.A satellite acquisition algorithm based on CUDA platform is proposed to solve the problem that the acquisition algorithm contains a large number of FFT operations,which is time-consuming and inefficient.The powerful parallelism and floating-point computing ability of CUDA platform are used to accelerate the acquisition algorithm and reduce the running time of the acquisition algorithm.The acquisition algorithm of CUDA platform is faster than that of CPU only.4.Build the Beidou satellite software receiver simulation platform based on C language.The traditional satellite signal acquisition algorithm and the acquisition algorithm proposed in this paper are simulated,analyzed and compared.