Method and system for resolving the acquisition ambiguity and the problem of false lock in tracking BOC(n, n) modulated signals, particularly for satellite positioning/navigation systems

摘要

A method and a system for the acquisition and tracking of BOC (n,n) modulated codes are described, in which a correlation function is locally generated at a receiver terminal using a code w a according to the relationship w a ( Ä ) €‰ = €‰ c ( Ä n ) - €‰ a ‹ prn �¢ Ä n €‰ + T c €‰ €‰8 2 - €‰ prn €‰ Ä n - €‰ T c €‰8 2
wherein c(Ä) is a local replica of the BOC modulated pseudo-random noise code with delay Ä n , prn(Ä) is a replica of a unmodulated pseudo-random noise code, and a is a predeterminable weight coefficient.
Said correlation function is used in an acquisition test function according to the formula x BOC ( n ) - a ‹ x BOC �¢ / PRN ( n + 1 ) - x BOC / PRN �¢ n - 1 2
wherein x BOC is the autocorrelation function of the BOC modulated pseudo-random noise code acquired, and x BOC/PRN is the cross correlation function between said acquired BOC modulated pseudo-random noise code and the early and late local replica of the unmodulated pseudo-random noise code, respectively. Said test function is used to recognize a code acquisition, if a value of said test function is higher than a predetermined threshold.