A novel weak signal acquisition scheme for Beidou nGEO satellite signals

The presence of secondary codes on the top of primary codes to modulate Beidou nGEO satellite signals puts a constraint on the coherent integration duration for possible bit sign transition on the boundary of each primary code period. This paper address the problem of coherent integration over periods longer than one primary code length and the acquisition of NH code chip position. A scheme combining zero-padding with characteristic length of the NH code sequence is proposed to handle both these problems together.