Dual High-Resolution Correlators for Multipath Mitigation in BOC Signals

Multipath is a dominant source of positioning errors in global navigation satellite system receivers. It is difficult to design multipath mitigation techniques for binary-offset-carrier (BOC) signals due to the complicated autocorrelation function (ACF) of BOC signals and localized variations of multipath. In this article, a dual high-resolution correlators (DHRC) technique is proposed for BOC signals to mitigate code and subcarrier multipath errors, as well as the carrier multipath error that is neglected by common techniques. Based on the concept of dual binary phase-shift keying (BPSK) tracking, the BOC signal is decomposed into two BPSK signals located in the upper and lower sidebands, respectively, thereby transforming the multipath mitigation in the BOC signal into the multipath mitigation in the upper and lower sidebands. Two narrow correlation (NC) functions of the upper and lower sidebands are synthesized using multiple correlation values, so the multipath outside the main peak of the synthesized correlation function is eliminated. The peak value of the synthesized correlation function is reduced from the original ACF, resulting in a large noise error. Therefore, a complementary filter is designed to compensate the noise error. Theoretical analysis and simulation results demonstrate that the DHRC technique with complementary filters can significantly mitigate multipath errors for BOC signals with slight thermal noise performance loss.