Coherent Periodic Signal Acquisition for LEO Navigation: A Zak Transform Approach

In this letter, a high-performance coherent acquisition approach based on Zak transform is proposed for low Earth orbit (LEO) navigation signals. The approach correlates the received signal and local replica in delay-Doppler (DD) domain. By exploiting the correspondence between the circular shift of the periodic signal in DD domain and the channel Doppler, it effectively compensates for the Doppler offset and reduces signal-to-noise ratio (SNR) loss during stepwise Doppler search. Simulation results for direct sequence spread spectrum (DSSS) signals show a 0.8 dB sensitivity improvement over the state-of-the-art under maximum Doppler offset, the lowest complexity with less than 1 dB SNR loss, and a 56.1% reduction in mean acquisition time.