引入近邻约束的自适应门限M/N检测算法
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摘要
针对高动态、低载噪比环境下,捕获扩频信号会出现伪码相位与载波频率的动态迁移及相关峰值损耗较大等问题,研究了捕获系统中的检测判决模块。首先,通过分析捕获相关结果的统计学特性,确定了不同积累时间对应的自适应门限;其次,考虑信号的高动态特性,对多普勒频率造成的伪码相位偏移进行近邻约束;最后,将近邻约束条件和自适应门限判决方法应用到M/N检测算法中,若N次检测中有M次结果满足自适应门限条件和近邻约束条件,则判断信号捕获成功。理论分析表明,改进后的M/N检测方法在单次检测的虚警率固定时,可使系统的虚警率大幅降低,因此,该方法通过降低单次积累的门限值,提高了检测概率,降低了虚警率。仿真结果表明,改进后的判决策略显著提高了捕获算法的灵敏度,改善了捕获性能。
In the high dynamic and low carrier-to-noise ratio environment,the dynamic migration of the pseudo-code phase and the carrier frequency will occur in the acquisition result of the spread spectrum signal,and the correlated peak loss is large.This paper studies the detection decision module in the acquisition system.Firstly,by analyzing the statistical characteristics of the correlated acquisition results,the adaptive thresholds corresponding to different integration times are determined.Then,considering the high dynamic characteristics of the signal,the pseudo-code phase offset caused by the Doppler frequency is constrained by neighbors.Finally,the neighbor constraint condition and the adaptive threshold decision method are applied to the M/N detection algorithm.If there are M times in the Ntimes of detection satisfying the adaptive threshold condition and the neighbor constraint condition,then the signal acquisition is judged to be successful.Theoretical analysis shows that the improved M/N detection method greatly reduces the false alarm rate of the system when the false alarm rate of a single detection is determined.Therefore,this method improves the detection probability and reduces the false alarm rate by lowering the threshold of the single integration.The simulation results show that the improved decision strategy significantly improves the sensitivity of the acquisition algorithm and improves the acquisition performance.
In the high dynamic and low carrier-to-noise ratio environment,the dynamic migration of the pseudo-code phase and the carrier frequency will occur in the acquisition result of the spread spectrum signal,and the correlated peak loss is large.This paper studies the detection decision module in the acquisition system.Firstly,by analyzing the statistical characteristics of the correlated acquisition results,the adaptive thresholds corresponding to different integration times are determined.Then,considering the high dynamic characteristics of the signal,the pseudo-code phase offset caused by the Doppler frequency is constrained by neighbors.Finally,the neighbor constraint condition and the adaptive threshold decision method are applied to the M/N detection algorithm.If there are M times in the Ntimes of detection satisfying the adaptive threshold condition and the neighbor constraint condition,then the signal acquisition is judged to be successful.Theoretical analysis shows that the improved M/N detection method greatly reduces the false alarm rate of the system when the false alarm rate of a single detection is determined.Therefore,this method improves the detection probability and reduces the false alarm rate by lowering the threshold of the single integration.The simulation results show that the improved decision strategy significantly improves the sensitivity of the acquisition algorithm and improves the acquisition performance.
引文
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[14]马琳,崔嵬,吴嗣亮.极低信噪比环境下含近邻约束的改进唐检测判决算法[J].系统工程与电子技术,2011,33(8):1 745-1 749.(MA Lin,CUI Wei,WU Si-liang.Improved tong multiple trial algorithm with near neighbor contraint in extremely low SNR condition[J].2011,33(8):1 745-1 749.)
[15]STEVEN M K.Fundamentals of Statistical Signal Processing Volume I:Estimation Theory[M].Prentice Hall,1993.
[2]POLYDOROS A,WEBER C L.A unified approach to serial search spread-spectrum code acquisition-Part I:General theory[J].IEEE Trans Commun,1984,32(5):542-549.
[3]刘嘉兴.发展Ka频段测控通信系统的思考[J].宇航学报,2008,29(6):1 685-1 688.(LIU Jia-xing.Ideas on development of Ka band tracking,telemetry,command and communication system[J].Journal of Astronautics,2008,29(6):1 685-1 688.)
[4]于志坚.载人航天测控通信系统[J].宇航学报,2004,25(3):247-250.(YU Zhi-jian.TT&C and communication system of Chinese manned space flight[J].Journal of Astronautics,2004,25(3):247-250.)
[5]FU Z,HORNBOSTEL A,HAMMESFAHR J,et al.Suppression of Multipath and Jamming Signals by Digital Beamforming for GPS/Galileo Applications[J].GPS Solutions,2003,6(4):257-264.
[6]REICHERT A,AXELRAD P.GPS carrier phase multipath reduction using SNR measurements to characterize an effective reflector[C]//Proceedings of International Technical meeting of Satellite Division of the Institute of Navigation,1999:1 951-1 960.
[7]LIU J S,CHEN R.Sequential Monte Carlo methods for dynamic systems[J].Journal of the American Statistical Association,1998,93(443):1 032-1 044.
[8]谢钢.GPS原理与接收机设计[M].北京:电子工业出版社,2009.(XIE Gang.Principles of GPS and Receiver Design[M].Beijing:Publishing House of Electronics Industry,2009.)
[9]KAPLAN E D,HEGARTY C.Understanding GPS:Principles and Application[M].2nd ed.Boston:Artech House Publishers,2006:166-170.
[10]OMAHONY N,MURPHY C C.Constrained optimization of coincidence detector parameters for GPS acquisition[J].IEEE Trans Commun,2012,60(1):176-188.
[11]WARD P W.GPS receiver search techniques[C]//IEEE Position Location and Navigation Symposium,1996:604-611.
[12]RAVI K V,Ormondroyd R F.Computer simulation of a quantized log-likelihood sequential detector for faster acquisition of spread spectrum pseudo-noise signals[C]//IET International Conference on Radio Receivers and Associated Systems,1990:207-211.
[13]陈景霞,李建文.新的全球定位系统弱信号高灵敏捕获算法[J].计算机应用,2012,32(11):3 262-3 267.(CHEN Jingxia,LI Jian-wen.New GPS weak signal high-sensitivity acquisition algrithm[J].Journal of Computer Application,2012,32(11):3 262-3 267.)
[14]马琳,崔嵬,吴嗣亮.极低信噪比环境下含近邻约束的改进唐检测判决算法[J].系统工程与电子技术,2011,33(8):1 745-1 749.(MA Lin,CUI Wei,WU Si-liang.Improved tong multiple trial algorithm with near neighbor contraint in extremely low SNR condition[J].2011,33(8):1 745-1 749.)
[15]STEVEN M K.Fundamentals of Statistical Signal Processing Volume I:Estimation Theory[M].Prentice Hall,1993.