Unambiguous Tracking Technique Based on Sub-Carrier Pulse Grouping for TMBOC-Modulated Signals in GPS

Based on grouping the pulses that compose the sub-carrier of the time-multiplexed binary offset carrier (TMBOC), we present an unambiguous correlation function that has no side-peaks causing the ambiguity in the TMBOC signal tracking, and also, that has a higher degree of the sharpness of the main-peak (DSM) over those of the conventional unambiguous correlation functions. Splitting the pulses composing the TMBOC sub-carrier into 12 groups, and, subsequently, forming the 12 group correlations corresponding to the 12 groups, we investigate the contribution of each of the 12 group correlations to the side peaks and main peak of the TMBOC autocorrelation function. Then, we propose a combining method of the 12 group correlations based on the investigation to remove the side peaks while improving the DSM. Numerical results demonstrate that the proposed unambiguous correlation function not only has no side-peaks, but also has a higher DSM, and, consequently, has a better tracking error performance than those of the conventional unambiguous correlation functions.