| As a new modulation technology,BOC modulation has been widely used in GNSS navigation systems,and the splitting characteristics of the power spectrum and the narrow correlation peak characteristics of the correlation function can avoid spectral aliasing between BOC modulation signals and other signals,and improve the frequency band utilization.In addition,BOC modulated signals have better resistance to multipath than traditional BPSK modulated signals.However,the multimodal nature of the autocorrelation function of the BOC modulation signal will lead to signal miscapture,resulting in capture failure.This paper focuses on this issue,and the work content is as follows:Firstly,this paper introduces several satellite navigation system modulation technologies,involving BPSK modulation technology,BOC modulation technology and derivative MBOC modulation technology.The modulation principle is introduced and the signal characteristic parameters such as power spectral density,autocorrelation function and phase discrimination curve of the modulated signal are analyzed with the help of the MATLAB simulation platform.In addition,the principles and performance of classical algorithms such as the classic BPSK-Like algorithm,ASPeCT algorithm,and SCPC algorithm are analyzed and explained.Secondly,aiming at the problem of blurring of BOC modulation signal capture,a fuzziness-free algorithm based on split reconstruction correlation function is studied.The local BOC code is divided into four parts equidistant to correlate with the input IF signal,four sub-branch correlation vectors are generated,the four correlation vectors are reconstructed,and finally the detection correlation peak without side lobe edge peaks is obtained,which completely eliminates side lobe interference.The sine and cosine BOC(1,1)modulated signal was used as the simulation signal,and the performance comparison experiment was carried out with ASPeCT algorithm,SCPC algorithm and BPSK-Like algorithm.Experimental results confirm that the proposed algorithm has better defusity effectiveness and better multipath resistance than the three classical algorithms.Finally,aiming at the problem of ambiguity of MBOC modulation signal capture,a fuzziness-free algorithm based on reconstructed correlation function is studied.Using the digital characteristics of the autocorrelation function of MBOC modulation signal,the crosscorrelation function between MBOC modulation signal and local pseudocode and BOC modulation signal is generated by referring to the reconstruction process of ASPeCT algorithm,and finally the ambiguity of the captured peak is eliminated through the reconstruction rule proposed in this paper,and a detection correlation peak without side lobe edge peak is obtained.The performance of the reconstructed algorithm is compared with ASPeCT algorithm,SCPC algorithm and BPSK-Like algorithm,and it is verified that the capture performance and anti-multipath performance of the reconstructed algorithm are better than those of the classical algorithm,and its detection peak is steeper and the peak value is larger.The detection probability value is also higher than the three classical algorithms;When the signal-to-noise ratio is-29 d B,it is improved by 8.09%,15.92% and16.42% compared with the classical algorithm,respectively. |
