Acquisition Of Beidou Weak Signal In High Orbit Environment

At present,high-orbit spacecraft autonomous navigation technology has become one of the new technologies that are urgently needed for the improvement in China,and the application of navigation receivers in high-orbit spacecraft has become a hotspot in all kinds of engineering works.The major difference between a high-orbit navigation spacecraft receiver and a terrestrial receiver is that the former needs to receive navigation satellite signals from the opposite side of the earth.The increasing signal propagation path has caused many problems such as large path loss and weak reception signal.Therefore,it becomes pretty necessary to carry out the research on the weak signal capture technology of high-orbit Beidou.In this paper,the characteristics of the Beidou signal are simulated,which can confirm the received power threshold of the weak signal acquisition algorithm.In the area of signal search,the advantages and disadvantages of serial acquisition algorithm and FFT-based parallel code phase acquisition algorithm are analyzed.As for the process of gain accumulation,the coherent accumulation,non-coherent accumulation and differential coherence accumulation are compared and analyzed.On the elimination of the data code phase hopping,this paper analyzes half-bit and full-bit accumulation methods.Aiming at the problem that the traditional differential coherence algorithm is not suitable for the full bit accumulation algorithm,this paper puts forward a differential coherence algorithm based on the full bit,which has solved the problem that the signal cannot accumulate for a long time,thus improving the processing gain of the Beidou weak signal.The traditional non-coherent algorithm and the improved algorithm are simulated respectively by MATLAB,which proves that the improved one has obvious performance advantage in Beidou weak signal acquisition.At the same time,the minimum signal power of the improved algorithm is simulated,and the simulation results show that the improved algorithm can realize not only the capture of weak signal of-175 dBW but also the capture of weak signal with signal power that low to-178 dBW,which can meet the technical requirements of this subject.