An Optimizing Combined Unambiguous Correlation Functions for BOC Signals Tracking

Abstract

The binary offset carrier (BOC) signal possesses split spectrum and narrow main-peak in autocorrelation function (ACF). BOC modulation can separate the new designed signals from the existing signals, and it also has better code tracking performance and improved capacity of multipath mitigation. Therefore it has been widely applied in the modernized global navigation satellite systems (GNSS). However, false locking may be generated in the acquisition and tracking procedure due to multiple side-peaks in BOC autocorrelation function, which is a challenge for the future receiver. In this paper, a new unambiguous tracking technique based on the optimized combined ACF of BOC signals is presented. This technique generates multiple replicas of BOC signals with different time delay in the receiver, and the multiple replicas are correlated with the received signal, then an unambiguous combined correlation function is derived by weighting and adding the outputs of correlators .The weighting coefficients are derived from numerical optimization algorithms for better performance. By multiplying the correlation result mentioned above with the ideal BOC signal autocorrelation function, the unambiguous non-coherent correlation function is obtained. Simulation results show that proposed technique can completely remove the side-peaks from the ACF of BOC signals while still keeping the sharp main-peak, which maintains the tracking accuracy property of the BOC modulation. And also the performances in terms of multipath error envelope are evaluated, our method has the similar multipath mitigation performance with the traditional method and better than the BPSK-like.