An Unambiguous Multipath Mitigation Method Based on Double-Delta Correlator for BOC Modulation Signal

Abstract

With the development of global navigation satellite system (GNSS), binary offset carrier (BOC) modulation signal has been widely used for GPS and Galileo. However, because of the effect of the subcarrier, the autocorrelation function (ACF) of BOC signal has a main peak and some side peaks. The traditional delay-locked loop (DLL) may be locked on the side peaks of ACF, which causes an extra tracking error. Dual-estimate loop method is an effective unambiguous tracking method, which makes use of two DLLs to track the code phase and the subcarrier phase in BOC signal. However, the multipath effect is not taken into account for dual-estimate loop method. This paper proposes an unambiguous multipath mitigation method, which employs the dual-estimate loop method to solve the tracking ambiguity problem for BOC signal and makes use of double-delta correlator in the subcarrier tracking loop to mitigate the multipath effect. In addition, a bias code delay estimate value is used in the subcarrier tracking loop to enhance the performance on the multipath mitigation. Simulation results demonstrate that the proposed method can provide the same level of tracking performance as the traditional DLL tracking technique in the case of high carrier-to-noise ratio (CNR) and have the excellent performance on the multipath mitigation.