A closed-loop coherent PN acquisition scheme for DS/SS systems using an auxiliary sequence

We propose a closed-loop system for acquisition of the pseudo-noise (PN) sequence in direct-sequence spread-spectrum (DS/SS) systems. We introduce a novel idea of using an auxiliary sequence, as opposed to the PN sequence itself, for correlation with the incoming signal. The correlation function of the auxiliary sequence and the PN sequence has a triangle shape that covers essentially the entire period of the PN sequence. Consequently, their correlation provides the direction for the phase update of the local sequence generator in the acquisition scheme. With coherent demodulation, the average acquisition time of the proposed scheme is derived and is compared to that of the conventional serial-search acquisition receiver. Results suggest that the proposed system acquires PN phase at least twice faster