Impact of the group delay on BOC(M,N) tracking: Potential filter issues in robust side-lobe switching for high-order BOC modulations

This paper discusses some technical problems and proposes a solution related to the implementation of a robust switching between single-side and double-side lobe tracking modes in case of BOC modulated signals, in particular BOC(M,N), with M, N > 1. It is demonstrated that typical group delay distortions due to wide-band front-end filters can potentially lead to code tracking biases, increasing the risk of false locks and degrading the performance of the BOC tracking loops. These effects represent also a potential problem for the coexistence of the side-lobe switching functionality with other advanced algorithms in professional-grade GNSS receivers. These practical issues are investigated and a possible solution is demonstrated by means of simulation results, considering the BOC(M,N) modulations in the Galileo E1a and E6a bandwidths.