New Unambiguous Boc(n,n) Tracking Technique

Galileo and Modernized GPS have included in their signal structures a new signal modulation: the Binary Offset Carrier (BOC). In the navigation field, this modulation is characterized by the chipping rate of its spreading code (m×1.023 MHz) and the frequency of its square sub-carrier (n×1.023 MHz). As a consequence, it is usually referred to as a BOC(n,m) modulation. The choice of the parameters n and m has a significant impact on the signal tracking performance and characteristics [1]. It is well known that each BOC modulation brings many improvements when compared against a classical Bi-Phase Shift Keying (BPSK) modulation with the same chipping rate [1]. Among other examples, it provides a lower code tracking error in thermal noise, better multipath mitigation, and better rejection of narrow-band interference. However, its multi-peak autocorrelation function is a major drawback. This implies that when using classical acquisition and tracking techniques, there is a possibility of detecting and tracking the signal by locking onto a side-peak. This can lead to severe undesirable measurement biases when not corrected.