基于差分相关积分的北斗弱信号快速捕获方法  

Fast acquisition of Beidou weak signal based on differential correlation

作　　者：韩志凤[1] 刘建业[1] 李荣冰[1] 高关根[2] HAN Zhi-feng LIU Jian-ye LI Rong-bing GAO Guan-gen(Navigation Research Center, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China AVIC Xi＇an Flight Automatic Control Research Institute, Xi＇an 710065, China)

机构地区：[1]南京航空航天大学导航研究中心,南京210016 [2]西安飞行自动控制研究所,西安710065

出　　处：《中国惯性技术学报》2016年第6期815-820,共6页Journal of Chinese Inertial Technology

基　　金：国家自然科学基金资助项目(61374115;61273057;61328301;61104188);中航工业产学研技术创新基金;南京航空航天大学博士学位论文创新与创优基金(BCXJ14-06);江苏省研究生培养创新工程(KYLX_0283);中央高校基本科研业务费专项资金资助

摘　　要：为了提高北斗接收机弱信号捕获灵敏度,解决数据比特跳变和NH码相位变化限制相干积分时间延长的问题,提出了一种基于复数型差分相关积分的北斗弱信号捕获算法。首先,在分析了北斗信号特点的基础上,对常用弱信号捕获算法进行数学分析;然后,设计了按照采样点进行延迟差分的复数型差分相关积分算法,采用正交采样方法获得复数型中频数据,利用FFT变换实现对码相位和载波频率的并行搜索;最后,利用软件接收机开展仿真验证,实现了5 ms、10 ms和20 ms的差分相关积分,积分后信噪比提升约7 d B、10 d B、13 d B。该算法极大地削弱了北斗信号比特跳变和NH码相位变化的影响,有效提高接收机弱信号捕获能力;采用基于FFT算法进行并行搜索,相比传统捕获算法极大地缩减了捕获时间,并适用于全部北斗信号和GPS信号,无需考虑GEO和非GEO导航电文的差异。In order to improve the acquisition sensitivity of Beidou receiver and solve the problem that the coherent integration time is limited by the data bit jump and the NH code phase change, a weak-signal acquisition algorithm is put forward based on differential correlation.Firstly, based on the characteristics of Beidou signal, some common weak-signal acquisition algorithms were analyzed.Secondly, a differential correlation algorithm with sampling point delay was designed.By means of an orthogonal sampling method, the complex intermediate frequency data was obtained, and then the FFT transform was used to realize the parallel search of code phase and carrier frequency.Finally, the simulation verification was carried out by using software receiver, which shows that the differential correlation integrations of 5 ms, 10 ms and 20 ms are realized, and the signal-to-noise ratio is increased by about 7 d B, 10 d B and 13 d B, respectively.This algorithm greatly weakens the influences of NH code phase change and Beidou signal bit jumps, and can effectively improve the receiver＇s acquisition capacity for weak-signals.Compared with traditional algorithm, the parallel search algorithm based on FFT algorithm can significantly reduce the acquisition time, and is applicable to all kind of Beidou and GPS signals without considering the navigation message differences between GEO and non-GEO.

关 键 词：快速捕获 NH码 北斗接收机 高灵敏度 弱信号 

分 类 号：V249.3[航空宇航科学与技术—飞行器设计]