交替二进制偏移载波(AhBOC)调制信号的自相关函数具有多峰性,导致全球导航卫星系统(GNSS)接收机同步阶段容易产生误捕和模糊跟踪。针对此问题,首先建立了AhBOC信号的模型,并在此基础上提出了一种基于合成相关函数的AltBOC(15,10)信号无模糊跟踪方法。该方法通过设计两路本地辅助信号的波形,与接收AltBOC信号进行相关运算,构造出无边峰的合成相关函数,实现无模糊跟踪。理论分析与仿真结果表明,该方法能够完全消除AltBOC信号自相关函数边峰,保持了主峰的宽度,有效地提高了码跟踪的可靠性,同时具有较好的多径抑制能力。
False lock and ambiguous tracking may be generated in the synchronous process of the Global Navigation Satellite Systems (GNSS) receivers due to the multiple side-peaks in autocorrelation function (ACF) of the alternative Binary Offset Carrier (AltBOC). To solve the problem, the framework of AltBOC modulation was designed, and an unambiguous tracking method was proposed based on a combined correlation function for AltBOC (15, 10) signal. This new method was implemented to create a no-side-peak combined correlation function by designing the modulated symbols of two local signals, which were cross correlation with the received AhBOC signal. The theoretical analysis and simulation results indicate that the proposed method can remove the side-peaks of AltBOC ACF completely while maintaining the shape of main peak, thus the tracking reliability is improved effectively, and it exhibits an average multi-path performance.