Patent ID: 8630331

Claim:
A method for the acquisition of a direct-sequence spread spectrum signal, which is transmitted on a carrier frequency, and which is modulated with a code signal of length equal to Nc chips, for determining a code delay of said spread spectrum signal and a Doppler shift with respect to said carrier frequency, said determination being performed on a discrete two-dimensional space of M possible code delays and F possible frequency shifts, the method comprising: receiving and sampling said spread spectrum signal to obtain a sampled spread spectrum signal; performing a despreading operation of said sampled spread spectrum signal with a local replica signal of said code signal, by performing said despreading for a plurality of possible code delays between said sampled signal and said local replica signal, wherein the despreading includes despreading using consecutive long segments of the sampled signals, the long segments being of a length N, where N is a submultiple integer of a sample number denoted by M of the local replica signal, a number Mn of the despreaded segments of the sampled signals being given by Mn=M/N; by performing a step of computing a Fourier transform, wherein said frequency search is a parallel frequency search performed on a result of said despreading operation, and said Fourier transform is a fractional Fourier transform performed on said result; and performing, using each of said Mn segments of the local replica signal, the despreading for N possible successive delays between said local replica signal and said sampled signal.