An Unambiguous Correlation Function Using Partial Correlation for Frequency Hopping-Binary Offset Carrier Signals

Binary offset carrier (BOC) modulation is a method of adding sub-carrier modulation to a signal with binary phase shift keying (BPSK) modulation. Compared to the correlation function of the BPSK-modulated spread signal, the main peak of the BOC signal is sharper. Sharper main peaks, are less affected by the multipath. However, the correlation function of the BOC-modulated spread signal has several side-peaks along with a sharp main peak, which easily causes false-locking during code tracking; this is reffered to as the ambiguity of BOC modulation. A frequency hopping (FH)-BOC modulation scheme is hence proposed to reduce the ambiguity of the BOC signal. However, many false-lock points still appear in the correlation function of the FH-BOC-modulated spread signal. In this study, to reduce the ambiguity of the FH-BOC-modulated spread signal, we propose an unambiguous correlation function using partial correlation. Compared to the FH-BOC-modulated signal, the proposed scheme has almost no false-lock points and is less affected by the multipath. From the simulation results, the highest value of the running average of the multipath error envelope (MEE) of the FH-BOC-modulated signal was about 0.822 m, while the highest value obtained with the proposed scheme under same conditions was about 0.524 m, about 36.2 % lower. © ICROS 2022.