On synchronization of Doppler-stretched GPS signals

The problem of synchronization of Doppler-stretched GPS signals is addressed. A new synchronization technique for the course acquisition code is proposed, which does not assume that the so called narrow-band condition is satisfied. Thus, the Doppler effect is modeled as a frequency shift on the carrier and a stretching of the complex envelope. As a consequence, observation intervals significantly longer than those adopted in conventional techniques can be adopted leading to a higher immunity against disturbance signals. The proposed technique exploits the cyclostationarity of the received signal and the fact that transmitted and received signals are jointly spectrally correlated. Simulation results show the better performance of the proposed method with respect to the conventional technique that models the Doppler effect just as a frequency shift of the carrier.