A closed-loop coherent acquisition scheme for PN sequences using an auxiliary sequence

Abstract

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