Abstract: A method for acquiring a direct sequence spread spectrum signal, which is transmitted on a carrier frequency and is modulated with a code signal of length equal to Nc chips, for determining a code delay of the spread spectrum signal and a Doppler shift with respect to the carrier frequency, the determination being performed on a discrete two-dimensional space of M possible code delays and F possible frequency shifts, includes: receiving and sampling the spread spectrum signal to obtain a sampled spread spectrum signal; performing a despreading operation of the sampled spread spectrum signal with a local replica signal of the code signal, by performing the despreading for a plurality of possible code delays between the sampled signal and the replica signal; and performing a parallel frequency search on the result of the despreading step, by performing a step of computing a Fourier transform on the result. The Fourier transform is a fractional Fourier transform.

Abstract: A method for acquiring a direct sequence spread spectrum signal, which is transmitted on a carrier frequency and is modulated with a code signal of length equal to Nc chips, for determining a code delay of the spread spectrum signal and a Doppler shift with respect to the carrier frequency, the determination being performed on a discrete two-dimensional space of M possible code delays and F possible frequency shifts, includes: receiving and sampling the spread spectrum signal to obtain a sampled spread spectrum signal; performing a despreading operation of the sampled spread spectrum signal with a local replica signal of the code signal, by performing the despreading for a plurality of possible code delays between the sampled signal and the replica signal; and performing a parallel frequency search on the result of the despreading step, by performing a step of computing a Fourier transform on the result. The Fourier transform is a fractional Fourier transform.