A differentially coherent delay-locked loop for spread-spectrum tracking receivers

Abstract

A novel differentially coherent delay-locked loop (DCDLL) for accurate code tracking is proposed for direct sequence spread-spectrum systems. Due to the use of the differential decoder and exactly one correlator, the proposed scheme avoids the problems of gain imbalance. The tracking error variance is derived by linear analysis. When the proposed DCDLL scheme is applied in ranging with additive white Gaussian noise (AWGN) channel, the performance of the proposed DCDLL scheme is about 1.4 dB better than that of one-correlator tau-dither loop (TDL), and near that of the noncoherent DLL.