FFT Sign Search with Secondary Code Constraints for GNSS Signal Acquisition

New GNSS signals are usually characterized by the presence of secondary codes and high data rates that can make the sign of the transmitted signal change each primary code period. Therefore, in order to extend the coherent integration time, relative signs between subsequent portions of the incoming signal have to be estimated and used to remove the effect of sign transitions. In this paper the problem of testing all the possible sign combinations is addressed and efficient FFT-based algorithms, suitable for different situations, are proposed. The algorithms proposed take advantage of the structure imposed by secondary codes and the case of composite GNSS signals, made up of data and pilot channels, is considered. Preliminary results based on live E5a GIOVE-A data are also shown.