Aiming at the tracking ambiguity of Alternate Binary Offset Carrier (AltBOC) (15, 10) signal caused by the multi-peak of autocorrelation function, an unambiguous tracking method based on combined correlation function was proposed. Firstly, two special local reference signals were designed in this method, then the correlation operations between the local reference signals and the received signals were realized through the code tracking loop to obtain two cross-correlation functions, and finally the ambiguity was eliminated through the unambiguous correlation function which is the multiplication of the two obtained cross-correlation functions. The tracking accuracy under thermal noise and anti-multipath interference performance of the proposed method were studied. The results show that:1) the proposed method realizes the unambiguous tracking; 2) the tracking accuracy of the proposed method is between Binary Phase Shift Keying Like (BPSK Like) method and Pseudo Correlation Function (PCF) method, and the tracking accuracy of the proposed method is nearly close to that of PCF method when the noise ratio is greater than 40 dB·Hz; 3) when the multipath delay is greater than 0.1 code chip, the proposed method has the multipath error significantly smaller than that of BPSK Like method and PCF method.

Binary Offset Carrier (BOC) modulation signal is a new type of satellite navigation signal with ingenious design. Eliminating the tracking ambiguity of signal is the premise of exploring its potentiality. Concerning the problem that the autocorrelation function of Cosine-phased BOC (CosBOC) signal is relatively more complex and difficult to express concisely and uniformly, as well as the lack of research on its tracking ambiguity, an unambiguous tracking method based on combined correlation function was proposed for CosBOC (10,5) signal in the E6 band of Galileo system. Firstly, a local reference signal of linear combination of as few local duplicated signals as possible and their shift weighted variants was designed, then through the code tracking loop, the reference signal was correlated with the received signal to obtain a correlation function without sub-peaks, eliminating the tracking ambiguity of code discriminator. Finally the code tracking error of the method was analyzed. The experimental results show that, compared with Binary Phase Shift Keying Like (BPSK Like) method, Bump Jump method and Pseudo Correlation Function (PCF) method, the proposed method has simple tracking loop structure, and it can suppress the tracking ambiguity completely and has better code tracking performance on the whole.