北斗B1C频点正交复用二进制偏移载波信号闸波设计方法

Strobe Pulse Design for Quadrature Multiplexed Binary Offset Carrier Modulation in BeiDou B1C Signal

第3代北斗卫星导航系统中B1C频点信号将使用正交复用二进制偏移载波调制方式。为了增强北斗卫星导航接收机码跟踪环路的抗多径性能并且解决码跟踪中的模糊跟踪问题,该文针对正交复用二进制偏移载波调制信号QMBOC(6, 1, 4/33)提出一种双闸波码跟踪环路结构。根据理想的目标鉴相函数和二进制偏移载波调制信号自相关函数的特点分别设计出针对BOC(1, 1)和BOC(6, 1)信号的闸波,并在本地码跟踪环路中使用这两种不同的闸波分别与输入信号相关,最后将所得的两个相关函数进行加权合并以用于鉴相过程。计算机仿真结果表明所提方法不仅能够有效消除QMBOC(6, 1, 4/33)信号的模糊跟踪可能性,且能够大幅增强接收机的抗多径性能,其对应多径误差包络面积相比于现有的方法能够减少约33%。

The third generation of BeiDou satellite navigation system employs Quadrature Multiplexed Binary Offset Carrier （QMBOC） modulation for B1C signal. In order to improve the anti-multipath performance of code tracking loops and solve the problem of code tracking ambiguity for BeiDou system, a double strobe code tracking loop structure for QMBOC（6, 1, 4/33） modulation is proposed. According to the ideal phase discrimination function and the auto-correlation function of BOC signal, two kinds of strobe pulse are designed for BOC（1, 1） and BOC（6, 1） respectively. Then, these two strobe pulse waveforms are used to correlated with the input signal in the code tracking loop. Finally, these two correlation functions are weighed combined for phase discrimination. The computer simulation results show that the proposed method can not only eliminate the code tracking ambiguity for QMBOC（6, 1, 4/33）, but also improve the anti-multipath performance dramatically： the multipath error envelope area is reduced by about 33% compared with the existed method.