基于分段匹配滤波与FFT的北斗信号捕获算法

BeiDou signal acquisition algorithm based on block matching filters and FFT

北斗B1I、B2I和B3I信号二次编码调制了速率为1kbps的NH码,频繁的数据比特符号跳变导致传统1ms相干积分峰值发生衰减和裂变,使得传统信号捕获算法错误率较高。针对此问题,提出了一种基于分段匹配滤波和快速傅氏变换（FFT）的北斗信号捕获算法。首先,分析了数据比特符号跳变对捕获算法性能的影响;其次,研究并设计了一种适合北斗信号的捕获算法,采用匹配滤波和FFT实现了对码相位和载波频率二维的并行搜索,和常规方法相比,信号处理效率和速度有了非常大的提高;最后,采用北斗中频信号采样数据对所提出的算法进行测试和验证。结果表明所提出的算法能够正确捕获北斗信号,消除了NH码相位的影响,不存在峰值裂变现象,该算法适用于北斗信号的捕获。

The navigation message of Beidou BII,B2I and B3I signals is modulated with a secondary code of NH code of 1 kbps. The frequent bit transitions result in attenuation of the traditional one-millisecond coherent integration. In order to solve this problem, a novel Beidou signal acquisition algorithm based on block matching filters and FFT is proposed. First, the problem that frequent bit transitions result in attenuation of the traditional one millisecond coherent integration is modeled and analyzed. Secondly, a novel Beidou signal acquisition algorithm is designed. With this algorithm, the code phase and carrier frequency can be estimated by parallel search. After analysis, this algorithm improves signal processing efficiency and speed compared with the traditional algorithm. Finally, a simulation test is carried out to verify the availability of the proposed algorithm. The results show that the signals can be acquired correctly without split and the influence of bit transitions is eliminated. This algorithm is suitable for Beidou signal acquisition.